#help-13
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so c is (-2,0)
done
now I need to calculate the area of apb
first find B
I can find it
good
what have you tried?
it comes 8/7 as m
sorry, was ordering food
now, we have 8/7, then we plug it into
(y-0)=8/7(x+2)
and find what's y when x=0
I got it y = 8/7+b
ok
so, what's b?
nah
do you know how this come from?
yeah you put y1 in y and the incline which is 8/7(-2) that is x1
no?
we plug y=0
no
it's x-(-2)
wait what is the equation
and that's y-coordinates of B
y=8/7(x+2)
so y=8/7(+2)+b?
yes
so how do we continue?
Time to find A so that we have baseAB
good
idk what is b
B is (0,16/7)
My brain just stop wroking after the (-2,0(5,8) fuss
yes
,calc 18*7-16
Result:
110
yes
ok and how can i find the height
8?
nah
5 is x
yes
so 5
yes
550/7
,calc 39*7+2
Result:
275
yes
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How do you solve this question?
I don't get the concept
@marsh glade are you having trouble understanding the questions ?
Yeah
Honestly I find them pretty unclear as well
Oh
Yeah
the other numbers are indications ok
so
The concept is you're presented with "axioms" of geometry and the exercise wants you to put them in practice
Oh
So do I need to know the "axioms" to solve this question?
The weird thing is it's not regular geometry, it's a "Fano Plane" so you have to use only the last 3 rules, not your own intuition
Yeah its confusing
Ok that explains it haha
Yeah haha
It's very niche geometry topic
It is
If this question is too confusing can I ask about another question?
the weird thing is I think l6 is a circle ๐
Don't worry I can help
Oh ok thanks so much
So if I understood correctly, you have 6 lines and seven points on the Fano Plane presented
The lines also include a circle which is confusing
Yeah
Yeah
That should be right
So what you need is to find out how the lines and points connect thanks to the drawing on the right
Oh
Honestly this feels more like graphs than actual geometry, are you familiar with graphs a bit?
Kind of
Not too well though
In discrete mathematics, and more specifically in graph theory, a graph is a structure amounting to a set of objects in which some pairs of the objects are in some sense "related". The objects correspond to mathematical abstractions called vertices (also called nodes or points) and each of the related pairs of vertices is called an edge (also ca...
it looks like this
It's the typical exercise of projective geometry
Oh
Its just even if I try to use everything I learned it doesn't work
Your Fano Plane is basically a graph where lines can have more than 2 points on them
It's not graph theory
I can't seem to solve it
Oh
Ok I haven't heard about it thanks!
I mean this as a way to picture it, it's not really a graph ok
@marsh glade what have you tried for 1.?
I got some answers
So for points 1 and 2 I did line 1 contains both, for points 2 and 7, I did line 5 contains both, and for points 5 and 6, I did line 2 contains both
I still don't get the violations of the first axiom part
The first axiom being that only one line goes through 2 points, none of the examples you gave violate it right?
Yeah
It can't violate it
Because theres no multiple lines that goes through 2 points at least from what I see
Oh
Right, exactly
But then the thing is question 2 starts to get me confused
Why should you? The axiom 1 holds
I don't get question 2: Which point is the intersection of line 1 and line 2? 3 line 4 and line 2? line 3 and line 6? Are there any violations of the second axiom?
Because there is no point that intersects line 1 and 2
Oh
I don't think there is any points unless I'm wrong
I would assume you get the intersection of l1 & l2 ; as well as l4 & l2. In practice they look like regular lines and the drawing shows they do in fact intersect right ?
Oh you don't see a point where they cross ?
Look at the picture and see which lines 1 belongs to.
Yeah
Ohhhh
I get it now
Awesome
Now question 3 and 4
Is making my life difficult
Q3: Why is it that regardless of which four points you choose, one point will not be on the same line as the other three?
Wait
The weirder one is l3 & l6 for question 2
Isn't the point where they intersect point 3
Not sure
would the answer be that 4 points are only coplanar but not colinear?
So since there is only 3 points for side of the triangle,
4 points cannot be all on the same line
They are ALL "coplanar" it's a Fano Plane haha
Oh
But no four points would be collinear right?
Yeah you're right that's the idea
exactly
I have never seen projective planes in geometry I'll check
Oh ok
Or maybe @high coyote can help
Oh wait I'm an idiot
The definition of a projective plane is the 3 axioms we saw
I thought that was the definition of the Fano Plane
You're welcome <3
So what you really want is to verify all 3 axioms on the Fano Plane, that way you will know that it is in fact a projective plane
Oh
But then would question three verify the third axiom?
Yes precisely
Fano Plane basically overkills the 3rd axiom by having all sets of 4 points non colinear
(1) (2) (3) is a possible definition of projective plane
I'd say it's a projectivization of a third-dimensional afine space tho. ๐
Oh
Oh ok thanks a lot
cool words :)
Awesome !! You did it
Yeah!!!!
Now I get what this question is
Thanks a lot guys
And about this - that's precisely the point of the exercise, so don't worry
Oh okay
Next time try to treat something new like you don't know anything and try to piece it out from scratch, then you should find similarities to other things you've done
Oh ok
Thanks
Also I have one more math question I want to ask
That way you're sure to not go in blindly thinking you know stuff you don't
Oh yeah
Should I ask it here?
sure
Its this
All of the questions I do are complicated
The thing is I feel like I can use a protractor, and at the same time, I feel like I don't need it
Yeah you're not supposed to
Oh ok
All the info is in the runway numbers
I still don't get
I think in this situation you need to get out a paper a pencil and draw out examples so you know you get it
Oh ok yeah I have a paper and pencil out
Wait for question 1, will the runway number be 21?
first you need to draw North because everything is based off of that
Oh
yeah I think you got the main idea
Try to draw 1, 36 and 27 for example
and 18
Oh ok
I'll give you an answer on my magnicent paint drawing ๐
Okay haha
Thanks
Are you good ? should i send my png ? @marsh glade
Yeah it would be great if you could
Thanks
I get it now
but I'm now stuck on question 2 and I have to get the value for angle 3 and 4
I got 1 and 2
which are 30 degrees and 150 degrees
Not sure if I am correct
What's the easiest way to calculate them with what you know already ?
You get the runway number and then you multiply it by 10 and then subtract it from 360?
Not sure
Yep I agree with those answers as well
Yeah so what's so different about 3 and 4?
Wait
I still can't solve 3 and 4
I don't get how the runway number will work using the same method I did for the other runways
The numbers are bigger
so like runway 33
yeah
Ok I see you're intuition, you're careful to not make a mistake by overgeneralizing
Yeah
So here it's fine as long your angles don't go over 360 and reset to 0
Because that's the only way your angle substractions will not work
Oh okay
Then for 3
like angle 3
will it be like 50?
50 degrees?
Because if the unknown runway number is 21,
the runway numbers are 15, 21 and 33 right ?
So if you put it all clearly like that you're unlikely to mess up
Was it really 50 ? between runways 15 and 21
I think I'm getting confused of finding the degrees
Wait no
Yeah it seems that way
60 degrees for angle 3 and 120 degrees for angle 4?
Because if you subtract 330 from 210 you get 120, and if thats angle 4 then angle 3 is 60?
(it seemed like you're measuring discrete intervals like between 1 and 3 strictly you have one integer but 3-1 is 2)
Oh
Yup perfect
Ohh okay
You need to crosscheck things when you get the chance, it lowers your amount of mistakes
Oh okay
Question 5 is just a lot of drawing: Airports are designed with more than one runway so that pilots landing planes will not have to deal with the difficult situation of landing in a strong crosswind. Design a runway system with the fewest number of runways so that a pilot will never have a crosswind angle of more than 30 degrees. Number each of the runways in your plan
I have to make my own runway system
Yeah the hard part is to interpret the question
Yeah I agree
"the fewest number of runways so that a pilot will never have a crosswind angle of more than 30 degrees"
Hmm
what spacing does that suggest you try
30 degrees spacing or less?
yeah
perfect
you can try and see if it works, and if you can prove it's the fewest amount of runways you won
Oh ok
Give me a minute
Let me try it out
Honestly it's been so fun helping you out, I'm really happy to do this
Thanks so much
I learned so much from today
That's awesome, my pleasure
yes that's the idea
Oh okay
but what about wind coming from the West?
Oh yeah
Then I would need to make one more?
Yeah
Would it be like this?
Or more like
this
Oh wait there is still a area
what about, wind at 61 degrees from North
that is larger than 30 degrees
yeah exactly
yeah?
this one actually works
try 61 degrees wind, which track would that be?
Hmm
like which runway?
ie smallest angle from wind
Or
Yeah because 90-61 = 29
so you get wind at 29 degrees
Oh yeah
Yeah ! Weird right?
Yeah!
Wait so it will still work if the angles are 30 degrees right?
So maybe our first idea for a solution wasn't the minimum amount of runways
Oh
Yeah of course, but is it minimal?
Maybe?
Well
this all 30 degree angles
Yeah
So which one is better, ie minimal amount of runways?
the minimal amount of runways?
Yeah which has less runways
This one
Yep
Ohhhhh
So then the other can't be our final answer yeah
Yeah
It's disproven to be our final answer
Yeah
Because while it works theres too many runways
Exactly
Any ideas to make our current best one even better? Is it really the best it can be?
I don't see any which can work to be even better
There might be a way
All right
But you need to consider wind from all four directions
That's good thinking
๐
Actually, is there only just 4 directions of wind?
No theres a lot more
From like southeast, northwest, southwest, northeast
Yeah
So any angle can be a wind angle
Yeah I agree
right
Honestly it's the kind of question where if you can find the best answer immediately you can justify that it's the best one
And the hard part is finding it
Oh yeah
Because even with our current runway system I feel like there is a way to get even less runways
It's kinda hard to brute force your way, but you can probably do it analytically
Yeah
Because what I drew is it all intersects at one point, but what if they intersect at different points?
It's just going to be more complicated
Nah we don't do that, remember runways are just angles and wind is just an angle so it doesn't matter
Oh yeah
Oh yeah
if you take another runway that runs parallel it will still have the same angle with the wind
Oh yeah so that won't work
Yeah
I can either give you a solution
or help you do it analytically (takes alot more time)
Thanks
So let n be the number of tracks, you have tracks $t_1, t_2, \cdots t_n$ integers between 1 and 36 that represent the track numbers (note : you can't have more than 36 tracks)
Mathospondylus
Yeah
I think even if you just give me a solution I can try to figure out how you got to that solution
The tracks are already in growing order so our problem translates to having the space between tracks ie $t_k -t_{k-1} \quad \forall k \in {2, \cdots n}$ to verify an equation
Mathospondylus
ok if you want
Sure but after you give me the solution can you just explain it to be simply?
Oh yeah haha
I would take the analytical approach if I had more time
But I need to go shower and to go sleep soon
haha
Thanks
I agree
actually it's algebraic my bad
Oh
Oh yeah haha
I get it now
Thanks so much!
I learned so much today
Sorry I gave you a red herring, I would have made the same mistakes on my own haha
starting from 30 degrees and realising it's not actually minimal
Oh no its fine haha
Oh yeah
Perfect! I'm glad I could help
I think thats all the questions today!
Before we go can I just send a friend request
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how to simplify
theres a few ways u can simplify
ๅผ ๅ ่ฑ
and then i cancel the threes?
the other way i can think of
is
u can split 8^(4/3) into 8^(3/3) * 8^(1/3)
which becomes 8 * 8^(1/3)
8^1/3 is the same as cuberoot of 8 which is 2
8*2 = 16
$8^\frac{4}{3}=8^\frac{3}{3}*8^\frac{1}{3}$
i think u meant to write 8^(3/3) lmao
ๅผ ๅ ่ฑ
uhm, $\frac{3}{3}*\frac{1}{3}\neq\frac{4}{3}$
ๅผ ๅ ่ฑ
ๅผ ๅ ่ฑ
oh
taro
anyway using this method ur thing would be
3sqrt(8^4)
i kinda forgot
i got the unstable foundation
think of it this way
does this work?
$2^3 * 2^4 = (2 * 2 * 2) * (2 * 2 * 2 * 2) = 2^7$
ah
taro
thats why we add the powers
idk why u cubed the 2 tho
its sll good exxept for the 2^3
wait no
ur right
wait
now im confusing myself
so what is $$\frac{8^{\frac{4}{3}}{8^{\frac{3}{3}}$$
oh right ur right
u just changed 8 to 2^3
yeye that works
๐๐ป
so u can turn it into a root
or play around w index laws
until u get smth easy to work with
up to you
ๅผ ๅ
่ฑ
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
hmm?
so what is (8^(4/3))/(8^(3/3))
taro
fgs good enough
yes
o
taro
have u learnt these index laws before?
$2^3^2$?
ๅผ ๅ
่ฑ
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
${2^3}^2$
taro
this?
yesyes
2^6
Is it $2^{(3^2)}$ or $(2^3)^{2}$? Parentheses matter when doing these problems
$({2^3})^2 = 2^3 * 2^3 = 2^6$
taro
2^5
im hoping he means the second one
MrFancy
whats the diffrence
if theres brackets
2^9
parentheses first :)
yep
npnp
great help
those r called the index laws if u need to learn them all
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is the inner function here (x^2+1) or sqrt(x^2+1)?
Wdym by inner function? If you mean under the root it's $x^2 +1$
physicsrocks
is that what I should substitute the u?
What's the question? Is this an integral?
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Hello! I have a question in discrete calculus. For a finite set of natural numbers S, where |S| is the number of elements in S and ฯ(S) is the sum of all elements in S, find
!status
What step are you on?
1. I don't know where to begin
2. I have begun but got stuck midway
3. I got an answer but I'm told it's wrong
4. I got an answer and would like my work checked
5. I have a question about someone else's worked solution
6. None of the above
2
Show your work, and if possible, explain where you are stuck.
I started finding the possible partitions of the sums and find the ones where it would cancel out to eventually find a pattern
For example {1,2,3} and {1,5} would cancel out in that expression
Since they have the same sum but the parity of the number of elements is different
I looked for the sums of the first 12 numbers but itโs very random
The ones where the sums donโt cancel out are 2,5,7,11, and 12
Itโs calculus for integers
I know it doesnโt add much lol
Where did you find this exercise ?
Did you solve it?
Btw Iโm not asking for a solution Iโm just trying to find a hint to move forward
Yeah I tried to reason using the clue but should I do it on sigma(S)?
What did you find with the clue
Well there would be 10 derivatives and since the maximum degree is also 10 it means that I should only reason on x^10
All the other ones with a degree less than 10 would just disappear
Arenโt you copying the forum ?
I checked the forum later on but I kinda got that on my own
I already have a good background in calculus
I know how derivatives work
Iโm just really new to discrete calculus
You find the degree of the polynomial try finding the dominant coefficient
Think of Ponchammer polynomial
@hot sigil Has your question been resolved?
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Triangle ABC is an isosceles triangle in which AB = AC. Side Ba is produced to D such that AD = AB. Show that angle BCD is a right angle.
Please don't occupy multiple help channels.
please delete either this channel or the other channel you are occupying
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Bruh
name the angle at B as alpha. write the angle BAC in terms of alpha, writhe angle CAD in terms of alpha, write angle ACD in terms of alpha. then it is obvious.
What is term of alpha
note A is circumcenter of ABC and midpoint is only circumcenter when triangle is right by Thales
if angle aBC = alpha what is angle BAC?
Bruh this is the Triangle lesson question
and what do you want to tell us with this?
That I don't know who is alpha ; - ;
name it x, or s or whatever you want.
the angle at B
ABC is isoceles, right?
Yes
what does this mean?
Abc and acb are equal
ok. and what else?
Don't know
What about triangle ADC
Acd and adc are equal
isoceles means: two sides are equal, and therefore the opposite angles are equal. and its a triangle. su the sum of all angles is ...?
What else ?
180
so the angle at BAC = ....?
angle ABC = angle BCA (as isoceles) and angle ABC + angle BCA + angle BAC = 180, so you get angle BCA = 180 - 2 x angle ABC
I think you also have angle bac=angle dac ?
Wat
what do you not understand?
But it is coming bac is equal to 180 - 2x
thats what i said.
now, what does this mean for angle CAD?
Angle cad is equal to 180 - 2y
what the fuck is y?
Variable
forget it. BAC = 180-2x, BD is a straight line, so CAD = 180-(180-2x) = 2x
Ok ok got
Wait
I think I can solve it now
Gimme 5 min
@nimble veldt hey
I cant
Find it
you have one angle in CAD (2x), triangle CAD is isoceles, so two angles (the 2 unknows) are equal, and the sum is 180. so the angle ACD is ,,,,
X?
CAD + ACD + CDA = 180, now use CAD = 2x and ACD = CDA, so you get 2x+2ACD=180 -> ACD = ...
90 - 2x
no
45 - x
no, 2x+2ACD = 180 -> 2ACD = 180 - 2x -> ACD = 90-x
and for the final step. sum up ACD and ACB.
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My lecturer asks us to "Discuss" theorems such as the Mean value theorem. I am not sure what this means, but he says he does not want us to define it or calculate the MVT for a function. What must we do when he asks us to "Discuss"
think about what it means. try to find interpretations. try to understand for what each of the prerequisites is necessary.
so you asked him what he wants you to do, but he ONLY told you what NOT to do?
Exactly
sounds like a purposefully unhelpful teacher who wants you to fail.
Thank you this helps, but I feel like he still might want more than this.
he wants you to learn and understand the mean value theorem. do you have qeustions? ask them in a group with your colleagues. and discuss them.
there are no qeustions for you? try to explan the questions from your colleagues.
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How to solve the equation set 2x + 3y = 2, -3x+2y=10?
do I begin like 5(2x+3y)=-3x+2y or?
because that becomes "13y=-13x", thusly y=-x
well i found the solution, x=-2 and y=2
๐
.close
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am i correct?
ping me when you reply plz
csc is cosec?
.
yes
yes, youre correct
yes
alr ty
@misty notch Has your question been resolved?
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Why is (b) is not a partial order and (c) is not a total order ?
I found that b is reflexive, transitive and anti-symmetric thus it shall be a partial order ?
help i need to submit tomorrow
Please read #โhow-to-get-help
Because people don't read server instructions
some people read the server instructions and actively choose not to follow htem
I need some time to process your answer
Could you show your reasoning behind why the relation in b is anti-symmetric?
Well if for instance |1| =< |2| then not |2| =< |1|
The only case when that happens is when a = b
For instance |1| = |1|
How about the fact that |-1| <= |1| and |1| <= |-1|?
Yeah so in b if you have xRy and yRx then you have |x| <= |y| and |y| <= |x|
Meaning |x| = |y|
But that is as far as you can go
|x| = |y| means x = y or x = -y
Yes I see
For c I see that it is transitive, reflexive and for symmetry...
Well it looks anti symmetric
For anti-symmetry assume xRy and yRx meaning (|x| < |y| or x = y) and (|y| < |x| or x = y)
And I am trying to see if it's a total order
Now, we can't have |x| < |y| because it would contradict |y| < |x| and x = y at the same time
Meaning x = y is forced
Generally try to come up with a rigorous proof
Ok I am gonna do that next time
Hm, the answer sheet says that the relation in c is not a total order?
Ah I see
I found
You can't compare the nonzero numbers with opposite signs
E.g. you can't verify whether (-1)R(1) or (1)R(-1)
So it's not total
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I don't understand how to progress at all
We want to take notice to "If the least amount of material is to be used", which means we will be needing the surface areas of a cylinder as well
OH
lemme try
@pliant wedge I did this.. abomination
this was my idea initially
i got it through getting the area of each can
adding it all up together
right
then
substituted
h1 and h2 in respect to r
with these
I got those off of the volume formula
I'm not quite sure how to get to here now
But I think it might have something to do with min values of the function
Yeah that makes sense
@crimson sedge Has your question been resolved?
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find a linear transformation T:R^3 -> R^3 that maintains
I don't know how to solve this please help
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Pick a number between 1 to 1000 at random. Find the probability
that is neither divisible by 12 nor 15.
How i solve this? or learn to solve this
So we have to first find which all are divisible by 12, 15, 12 and 15 then substract from the total
does that sound good?
Every 4th and 5th multiple of 3 is a number divisible by 12 or 15
You have to find out how many such multiples there are, and then subtract that value from 1000. Dividing that value by 1000 would give you your answer
@toxic bison I found this youtube video, let me try that, send you the pic of the solution.
Sure
No of multiples of 15= $\lfoor{1000/15}$
oh okaqy
Yes, but that will not work. This is because there will be common multiples of 12 and 15
For example 60, 120, etc
I didnโt complete
My bad
You have find multiple of 15
similarly for 12
and substract their common multiples
To find common multiples= floor(1000/lcm(15,12))
@crimson sedge Has your question been resolved?
The LCM of 12 and 15 would be 60
so?
this driving me nuts, i am gonna go outside after this and get some food.
have i solved it correctly?
Just understand the logic first please
ok
I do not think so
So every 12th number is a multiple of 12
Every 15th number is a multiple of 15
Every 60th number has both factors
Makes sense?
yes
60?
Number of 12 multiples: 83
Number of 15 multiples: 66
Number of 60 multiples: 16
It is the LCM of 12 and 15
So total number would actually be 83+66-32
We are subtracting 16 because when we add the multiples of 12 and 15, we are adding 60 twice
arent we going to multiply 83 by 12?
got it
I don't see what that will get you
Can you share the question again please
This is your solution right. I need the question
Pick a number between 1 to 1000 at random. Find the probability
that is neither divisible by 12 nor 15.
Yes
So 117 of them are not divisible
Which means the answer is 117/1000 or 0.117
Did you understand the solution?
So, we are going to multiply the 12 and 15 by 83 and 66 respectively. Then subtract 60x16=960 which is the lcm of (12 and 15)
Why do you want to multiply them lol
See, we just need the number of factors right
We don't need to multiply for that
Every 12th number is a multiple of 12
How many such "12th numbers" are there in a 1000? Well, it is 83
yes
Number of factors of 12 + Number of factors of 15 - 2(number of factors of 60)
The same you can do for 15 and 60
That gets you the number of multiples
83 + 66 = 154
Then you can use this formula
Yes
154 - ?
2*16
We are multiplying 2 and 16
See
It depends on the question
Every multiple of 60 is a multiple of 12 and 15
Right?
yes
You need to make sure that the number is neither divisible by 12 or 15
Because if it is divisible by 12 and not 15, it does not fulfill the condition of the question
Because it states "neither"
Makes sense?
yes
The only time a number is divisible by 12 and 15 is when it is divisible by 60
True?
So you have to remove all 60 multiples
When you add the multiples of 12 and 15, multiples of 60 come with both of them
Leave 16 for now, I'll get to that part
yes
But you do not want mutliples of 60, so you have to subtract them twice
yes
Coz one for 12 and one for 15, because they both bring the 60 multiples with them
yes
Now how many multiples of 60 are between 1 and 999?
16
Well, the answer is 16
Yes
So you multiply 16 and 2, and then you subtract that value from the number of multiples of 12 and 15
Makes sense?
yes, it does ๐
83 + 66 - 32 = 117 is the answer?
Yes
But you need to find the probability right
So you need to divide that by 1000, because it is the total possible outcomes
yes
why
117 is the number of values that are divisible by both 12 and 15
We want the rest of the values
So we subtract it from the total
Get it?
117 divided by 883 is my answer
yes
That should be your answer
Anytime!
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I am having trouble with questions C F and G
