#help-38
1 messages · Page 9 of 1
Well you can probably pit this into wolfram
Look up what Lagrange multiplier/the Lagrangian is
You need to find one with 2 constraints
This calculus 3 video tutorial provides a basic introduction into lagrange multipliers. It explains how to find the maximum and minimum values of a function with 1 constraint and with 2 constraints.
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These are your constraints
but i dont have x, y, z
Your function is r(a,b)
It’s still multi variable
im so utterly lost you wouldnt believe it
so i cant just do the partial derivative and = 0?
Yeah because you also have some constraints on what a and b could be
It’s still similar process but now you have to think about your constrains
this is an expression without the constraints
Well that’s a different story
fuck
It’s still a pain 
fuckk
ive never seen/ used partial derivatives and now im doing this
can u give me any hints?
Unfortunately there’s no hint for you
Look here
And do basically what he did
Put things into wolframalpha
Hope for the best
There’s no hint because I’m not doing this
I don’t drink coffee :3
a beer?

@edgy cedar one thing, does this count as calc?
Yeah multi variable calc
cheers
@solid summit Has your question been resolved?
@solid summit Has your question been resolved?
yo @edgy cedar, im doing it now, and the video says he needs 5 eqn, so i need 4 (one less unknown, I only have a, b, lambda and u), what eqns do i choose?
@solid summit Has your question been resolved?
Don’t you need all of them? You need to solve for a and b
Tbh I haven’t done one of these in a while so I may have forgotten something
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is it A?
x = distance from lamp
y = shadow length
5 / (x+y) = 2/y
3y = 2x
3 * dy/dt = 2 * dx/dt
3 * dy/dt = 2 * 1.4
dy/dt = 14/15
my doubt is that my work didn't include the x = 10m
so I feel like this is wrong
or was that extra info
Are ye serioues rn bro
@paper pond #❓how-to-get-help
diagram btw
I think it looks good
so was 10m extra info?
interesting
In this case the similar triangles grow at constant rates
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I genuinely have no idea where to start or how to do this question?
Its part b which im struggling with
i would think about the two perfect squares that 75 is inbetween
so like whats the nearest square below 75
64 and 81?
64
yeah
so sqrt of 64 is 8 right
therefore n is 8
cuz an integer is just a non fraction or decimal whole number
u can verify this by using a calculator too
sqrt of 75 is around 8.66
and 8 <8.66< 9 is true
so its 8
@mortal sinew Has your question been resolved?
Thanks @sonic token
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hello
this is what it looks like
ya
my only problem is simplifying radicals with a fraction
wait but
this doesn’t
seem quite right
to me
eh but I’m doing it
in my head
so I trust that’s correct
here ill send my work
yeye
ohhhhh
yeye
fs
for this problem I have to use the double angle formulas
However when u multiply across there I don't know how they get that final answer
they multiplied the numerators to get the final numerator
and multiplied denominators to get the denominator
2 x 13 isn't 13
im confused rn
so they multiplied both fractions by 1/2?
both the numerator and denominator
They had a factor of 2 on both sides that they cancelled out
@glacial karma
oh so the denominator multiplied like 8 x 16
since the 2 reduced the first 16 into 8?
Yeah
how would u do that with a odd number tho
it's for my problem
Then you don't need to
ah alr
bruh then how is my shit wrong then
Were you originally supposed to have 7√13?
instead of √137
Or did you directly get √137
,w 11^2 - 4^2
@glacial karma
but adjacent is sqrt105
oml brooooo im dumb af
i added 16 instead of subtracting it
LOLLLLL
it be like that sometimes
sin is positive
indeed
oh but bc u multiply by cos which is negative then the answer becomes negative
true\
bros carrying me lol
lol
Wasn't this supposed to be negative
i just sent my first screen shot of the problem
ah ok
the radical is throwing me off
ohh wait
is the square root supposed to go away bc I squared it
monikanicity
yeah
It be like that sometimes
Simplify?
Including noticing the numerator is a multiple of 105
so rationalize the denominator
yeah rationalize denominator
so like do I do -840 - 89?
nah
-840 + 89?
no
nvm it won't work
like lets say if it was square root of 50
u could simplify it to 5 square root of 2
that;s what I meant
ah ok
wait what happened to the bottom
They don't disappear
but it cancelled?
u can't leave √ 105 at the bottom
√105 * √105?
well that's not how I would do it but yes
so do u add the 105 with the 89?
√x * √x = x always
ya
what's the bottom number
bc u have the 89 too
so when we multiplied the √ 105 with √ 105
we were left with 105
i mean 105
but u have that 89 left over
it's just multiplied by 105
so it's -8√ 105/89?
yeah
alr thx sm bro
you're welcome
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How do I solve x^3 + 4x^2 - 7x + 11 = 0?
guess
whats that
if it doesn't then youre kinda screwed
And what's that?
cubic formula
if a polynomial with integer coefficients has any rational roots, then those roots are all of the form ±(divisor of constant term)/(divisor of leading term)
;D
good ol cubic formula
Ooh, thx
have fun
@lament jewel don't tell me you don't know what RRT is given that youve been studying complex analysis and the likes 
LMAOOOO
@lament jewel is special

I'm tired . close
this is Ann’s fav
.close
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no way
this looks so alien
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I'm stuck on a calculus problem: f(x) = 7e^x sin x, [0, 𝜋]
I got 7e^x (sin x + cos x) but I need to get coordinates in the parenthesis instead of the derivative
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is this an error in the book? or
can I get someone to help me with my math problem in my channel or is there a queue that I need to wait for?
1.2/6
ohh missed that... thank you
You just wait
got it
.close
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Im not sure I'm understand what an element pf R^w is
is the sequence endless?
also is poposition 2.4.10 is Let dim(V) = dim(W). A linear transformation T: V -> W is injective if and only if it is surjective
from my limited understanding of this question I think dim R^w = R^w but R is not a linear transformation.
which is why it doesnt follow 2.4.10
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Why does an object accelerate if it is changing direction
Can someone explain to me pls
Velocity is a vector quantity that's why
I suggest you go to the sister physics server
haha doesnt really answer what im looking for
why is does it being a vectory quantity mean it accelerates
anyway have oyu got an invite to the phsyicc one
Velocity is changing
If velocity is changing, there is an acceleration involved
ahh
is there a way to differentiate the two accelerations
like acceleartion due to change of direction and acceleartion due to change of pseed
speed
it seems quite confusing
Changing direction relates to changing speed
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Can anyone help me with this question i just can’t figure out where to start
waltuh, what question waltuh
What is initial velocity? Final velocity and distance covered?
So you have u,v,s. To find a you can apply one of the three equations of motion.
Alright thank you
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let f(x)=ln(x)/2x, which value gives the maximum value of f(x)
a.)1
b.)sqrt(e)
c.)e
d.)e^2
for this question?
do i just differentiate f(x)
until i get the simplest expression
so if i do f''(x) ln(x)/2x
o ye
,w d/dx log(x)/(2x)
log=ln
,w d/dx' log(x)/(2x)
Wolfram Alpha doesn't understand your query!
Perhaps try rephrasing your question?
Click here to refine your query online
,w f''(log(x)/(2x))
Log is used as ln everywhere past highschool
,w d/dx 2(log(x)-3)/(2x^3)
Can I ask what you are doing?
What?
You differentiate once
Set it equal to 0
Those solutions are critical points
You can then verify what kind by for example differentiating again
yo
hi
im learning like horizontal transformations and vertical transformations
and im really confused
o
.close
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I am a beginner at math so I have trouble solving the problem.
I wanted to know what kind of theory I should study upon or any advice on solving my problem.
My problem is as followed.
A , B = Non zero positive integer (not a floating point)
I have a finite list of A-B pair , For example List = [{A1,B1} , {A2,B2} , {A3,B3} , --- {An,Bn} ]
I wanted to find how many pair is within a single pair (I wanted to group them together)?
My sample example data is as follow.
+----+-----+
| A | B |
+----+-----+
| 30 | 201 |
| 31 | 179 |
| 31 | 178 |
| 30 | 148 |
| 31 | 117 |
| 30 | 87 |
| 31 | 165 |
+----+-----+
{A1,B1} to {A6,B6} is in a single group and {A7,B7} is in another group.
{A1,B1} to {A6,B6} is in a single group because A1+B1 = 202 and
{A1+A2+A3+A4+A5+A6} = {30 + 31 + 31 + 30 + 31 + 30 } = 184 (which is less than B1 [201] )
{A7,B7} is another group because 184+A7 = 184 +31 = 215 (which is greater than B1).
After the end of the group {A6,B6} , I wanted to reset the process and start it from the start of next group {A7,B7} until I run out of the number of pairs in my list.
I wanted to find out the pair which is the start of the group {A1,B1} , {A7,B7}. Or is it at least possible to find out how many group will there will in my finite set of list.
Please tell me if you wanted me to clarify the detail of my problem or wanted me to rephrase it in another way.
well just add the numbers An until you are too big and then start new
Could you please tell me if there is set-based logic of adding a number until they are too big and start new?
I am actually performing a date calculation. The "A" column is actually a "date" and I wanted go find out how many date to get
do you want to do this in some kind of software? in your head? on paper?
I have written it in software and I wanted to verify if I am right
For example
+-------------+-----+
| Date | Day |
+-------------+-----+
| 2021-07-24 | 201 |
| 2021-08-24 | 179 |
| 2021-09-24 | 178 |
| 2021-10-24 | 148 |
| 2021-11-24 | 117 |
| 2021-12-24 | 87 |
| 2022-01-24 | 165 |
+-------------+-----+
In the above example (same as previous data) , I wanted to put "2021-07-24" to "2021-12-24" into a single group and so on
I am curious in whether I can mathematically determine how many group I should have in a list in order to verify the output of my program
well to mathematically determine that you would just add up the numbers. which is probably the same as what your program does
My program actually does use other way to find the group so is adding the numbers a good way to verify it?
I am not sure if there is actually edge case which invalid it (adding the number up). I can only guarantee that A and B are non zero positive integer
My program actually needed to find a start of the group. and then it perform other operation on the start of the group
I know my program is having a problem on some edge case so I thought I can verify it with math
just a simple
sum = 0
i=1
while sum <= B1
sum = sum+A_i
i++
end
return i``` or something should work
(I hope I don't have an "off-by-one" error in there)
I am using it in database so set-based logic is better for me
and am trying to find it more math-like way instead of procedural like
logic
I can calculate but the problem is I needed to know "n" value
can you do something likefor each n calculate sum(A1, ..., An) ?
I know that loops in databases are bad tho
unsafe and all that
that what I am concern about
My database loop take too long to run but this is a math channel so
I thought somone know a way to optimize it
by using math logic
well then the question you should have asked is "hey can someone in here optimize database code for me"
you didnt even mention that you are working in a database for 30 minutes
well that was my mistake.
I only have very basic knowledge about databases, definitely no clue how to optimize queries or stuff like that, sorry. maybe try it in #computing-software ? not sure. or maybe the CS server under #old-network
well I can optimize query but I thought there is similar problem in math (finding a group based on a certain condition) instead of adding up a number
well the condition here is based on adding numbers
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A metal brace sits at 55 degrees to the horizontal and reaches 4.2m
up a wall.
can someone help draw this out?
i struggle at making these type of diagrams and i think thats giving me the incorrect answer
In general in math, a drawing is only supposed to illustrate. If the accuracy of drawing is somehow crucial to get a correct answer, you're doing it wrong
the question is a metal brace sits at 55 degrees to the horizontal and reaches 4.2m up a wall. The distance between the base of the wall and the base of the brace is:
i know its either Sin or Cos but i can't tell what to use so i wanted to illustrate it to find it out
By "4.2m up a wall", do you mean:
a. The distance between the base of the wall to the point where the brace and the wall meet, or
b. the length of the brace itself?
the questions just says '4.2m up a wall' and i assume it means the brace is acting as the hypotenuse
Yeah, the brace is acting as hypotenuse and the wall forms 90 degrees angle to the ground.
right
But I think the phrase "reaches 4.2m up a wall" is ambiguous. Is the question already in English?
Can you show the photo of your textbook?
,rccw
it reaches 4.2 meters up the wall, meaning that its the opposite which is 4.2 meters. knowing this, should you be using cos(55) or something else?
oh
sin
right !
ok i appreciate it, these questions get around ma head sometimes despite not really being that hard
but thank you !!!
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How is this reflexive?
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How many real subsets of the three-element set {2; 3; 4}?
the answer is 6 although I do not know how to solve it
for example {2,3} is a subset
its a subset of {2,3,4}?
yeah
yes
though i would have said 7 is the answer. wouldnt {} also be a real subset?
that sais i assume real means proper
i see
i would have said 8 lol
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find a collection of points that meet the requirement:
|z-i| < 4
a disk with centre at i and radius 4, like (x)^2 +(y-1)^2 <16
method is , put z= x+iy and solve further
thnkas
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How did you arrive at this step?
Is 2 + 2cosx = 4 cosx?
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Do you know what $A \cap B$ means?
dldh06
@static pewter Has your question been resolved?
yes
yes
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i don't get the u-sub
i mean why sqrt(3) at the top instead of 1/sqrt(3)
Cuz dx = sqrt3 du
numerator
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✅
at the last step, i don't get why the constant they put before is 1/sqrt(3)
i would put sqrt(3)/3
well thats the same thing
$\frac{\sqrt 3}{3} = \frac{\sqrt{3}}{\sqrt 3 \cdot \sqrt 3} = \frac{1}{\sqrt 3}$
Denascite
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How do I draw a line on the horizontal axis
@wraith hinge Has your question been resolved?
<@&286206848099549185>
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how to prove that the derivative of x^2 is 2x without power rule
also im a bit confused on why it wouldnt be x
somebody already helped me iwth this, but im confused where he got the equation from
please help
Use $\frac{f(x+h)-f(x)}{h}$
Mezza
This is differentiation by first principles
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lels
🫤
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I don’t know how to do this please help
also I’m pretty sure your supposed to use Desmos to find the answer
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need help with 7 and 9 please 🙂
i know it’s simple just wanna make sure i’m doing it correctly
Conside like 16/5+4/1
Can you solve now
i think its division
Damm
yes it’s division
My eyes hurts lol
sorry it’s not that clear 😭
Flip it 16/5 x 1/4
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can someone help me how to find A
Pertama-tama turunkan dulu f
Saya mau lihat bagamana Anda menurunkannya
Tinggal masukkan x=1
udh tp mencari A nya bingung
@light scroll Has your question been resolved?
BlokirKominfo
Saya tidak baca aturan bahwa A harus bilangan bulat.
Kalau begini, tinggal bagi kasus untuk A bilangan ganjil atau A bilangan bulat
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This is a problem for Surfaces Defined Parametrically and Surface Area. I need to set up a double integral but im not sure how to do it and really confused with the fractions. Help please?
Z = 5-2x-2y
dz/dx = -2
dz/dy = -2
ok now let's set this up as a double integral in x and y
we have
$$\iint_{C} (5 - 2x - 2y) dx dy$$
where C is the ellipse
According to my notes it becomes int sqrt(1+ dx^2 + dy^2) dxdy
And i need to set the limits for the double integration
Is this correct?
yeah that's right, i made an error there
Its fine. I just dont know how to find the limits. Can i get some help with that?
yeah sure
observe this
x^2/36 + y^2/4
x^2/6^2 + y^2/2^2
(x/6)^2 + (y/2)^2 = 1
let x/6 = cos(t) and y/2 = sin(t)
(cost)^2 +(sint)^2 = 1?
Is that the dy component?
Mr. Gamer
we found that f_x = f_y = -2, so squaring that gives 4.
we get sqrt(1+4+4) = sqrt(9) = 3
$$\iint_{C} 3 dx dy$$
Mr. Gamer
Okay got it so far
now we have to change coordinates from:
(x,y) -> (r,t)
(using t for theta here, don't feel like typing greek rn)
are you familiar with the jacobian?
No im not. Never heard of it sorry
ok so what we have to do basically is find what our dA element becomes under a change of coordinate system
we have the equations:
x = 6rcos(t)
y = 2rsin(t)
for:
0<=t<=2pi
0<=r<=1
so basically we have to take the determinant to change:
dx dy -> f(r,t) dr dt
let me show you how that's done, latex for determinants is kind of painful so i'll write it out
Thank you
dx/dr = 6cos(t), dx/dt = -6rsin(t)
dy/dr = 2sin(t), dy/dt = 2rcos(t)
now all we have to do is take the determinant of this matrix:
| 6cos(t) -6rsin(t) |
| 2sin(t) 2rcos(t) |
what do you get
Matrix? is this linear algebra?
Oh I actually didnt take linear yet. Ill try it tho?
I know this is cross product but never did something so complicated. Only numbers
$\begin{vmatrix}a&b\c&d\end{vmatrix} = ad - bc$
Mr. Gamer
yeah you're right
so then when we perform the subtraction we get:
12r exactly
now we can finally set up the integral
$$\iint_{C} 3 dx dy$$
Mr. Gamer
Mr. Gamer
Is it possible to ask one more? if you have time.
ok sure
This is the question
And this is my work done so far
Im pretty sure i made a error somewhere but unsure whats wrong with it
alright so the bounds on your integrand look good
not too sure about the jacobian factor or the radicand however
let's double check that
can you see how we'd get that:
2x = rcos(t)
2y = rsin(t)
wait i see what it is
our radicand should be:
1+(2x)^2+(2y)^2
(Let x = rcos(t), y = rsin(t))
1+(2(rcos(t))^2+(2(rsin(t))^2
1 + 4r^2(cos^2(t)) + 4r^2(sin^2(t))
1 + 4r^2
It doesnt seem right. I got 157.53473
why are you getting a decimal instead of an exact answer
the exact answer is (pi(135sqrt(5)-1)/6
yeah that checks out
Says that it is wrong.
i think i see your error now
when z = 7, we have x^2 + y^2 = 0, so our lower bound for r is 0
when z = 11, we have x^2+y^2=4, so our upper bound for r is 2
@stable jacinth
sure
let's consider our original eqn
z = 7 + x^2 + y^2
it just gives us a single bound on z (z<=11), so we have to find the minimum value that z can attain
x^2+y^2 will always be nonnegative, so the minimum value for z is 7. when z = 7, we get:
7 = 7 + x^2 + y^2
0 = x^2+y^2
0 = r^2
0 = r
Our upper bound for z is given as z = 11, when that occurs:
11 = 7 + x^2 + y^2
4 = x^2 + y^2
4 = r^2
2 = r
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if x = $\sin \left( \frac{2\pi}{7}
\right) + \sin \left( \frac{4\pi}{7}
\right) + \sin \left( \frac{8\pi}{7}
\right)$ and y = $\cos \left( \frac{2\pi}{7}
\right) + \cos \left( \frac{4\pi}{7}
\right) + \cos \left( \frac{8\pi}{7}
\right)$ then find x^2 + y^2
Chochan
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
@split chasm
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How does question 2 work?
question 2? do you mean part b?
oh yeah
i dont quite get it
am i supposed to plug in the values of g into x or something
$\boxed{?}$ just seems to be another function
ℝamonov
for g(-1) substitute all xs in
g(x) = x^2 + 2x
with (-1)
and simplify
so then -1^2 + 2(-1)?
those are two separate problems
ohhh
okay
i thought you had to do it in the same equation
so after simplifying the equation it would be
g(x) = (insert equation)?
no
wha
how would i write it then?
for g(-1) substitute all xs in
g(x) = x^2 + 2x
with (-1)
wdym
you know how theres a letter before (x)
like f(x)
g(x)
things like that
it says ?(x)
do i just keep it as ?(x)
$\boxed{?}$
ℝamonov
and is the ?(x) = 2x^3-x^2+6 part of the g(x) = x^2 + 2x
or is that its separate thing
two different functions
oh okay
so do i follow the same value input for part A with the equation on the right
wdym
it says g(-1) and g(2)
i still don't get what you mean
do i input these values onto the equation on the right equation
in the image
you use the g(x) function when finding g(whatever)
you use the ?(x) function when finding ?(whatever)
no?
so what values do i use
whatever it tells you to use
yes...
for g(-1) substitute all xs in
g(x) = x^2 + 2x
with (-1)
for g(this) replace all xs ing(x) = x^2 + 2xwith (this)
g(🍎) = 🍎^2 + 2🍎
and i apply that logic for the rest right
for g(-1), performing the described action gets you
g(-1) = (-1)^2 + 2(-1)
and simplify to get the value they wanted
same idea for the rest yes
same idea
express in terms of x?
for g(this) replace all xs in g(x) = x^2 + 2x with (this)
your result will have x in it
ohhh okay
that makes sense now
thank you a lot
when i substitute value with x like
x-5
would it look like
x(x-5)^2 + 2?
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Find the largest volume of the rectangular parallelepiped with the maximum surface area among the rectangular parallelepiped that can be enclosed in a sphere. ( r = 1)
i set f(x,y,z) = 2xy+2yz+2xz subject to x^2+y^2+z^2=4
but i can't solve this
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just as a quick question if i have -x+1 and i insert for e.g. -3 than it would be -(-3)+1 and not -3+1 right? :0
yep
thanks! just wanted to make sure because i have like
f(k) : k + 1, if k ≥ 0
-k +1, if k < 0
so yea thank you <3
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Is this $\frac{x-1}{2(1-x)}$
Sup?
yes its like this
Well u cant cancel right away, you need to make the x-1 into 1-x or vice versa
how do I do that
recall that (a-b) = -(b-a)
so it becomes 2-(x-1)
Implicit multiplication usually has precedence over division, however, since that is convention, I would recommend putting parentheses around it just to make sure it's unambiguous
aight
right now you're saying 2 minus (x-1)
(which isn't equal to 2(1-x))
Well you can. This is true.
I do not know how to do it tho
what is 2*(-x) equal to?
-2x?
So, therefore, can you now transform 2(1-x) with this?
it should be
2-2x
well, this is true, but we want to get a factor of (x-1) here
to simplify the fraction
sorry I do not understand what you mean
so just use this in the expression
(but correctly)
so x?
2(-(x-1))
why the added parentheses
Because in the original, it's two times 1 - x
So after applying the property, we get two times -(x-1)
not two minus x-1
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it's given that AE = BE, AF = 3DF, and we need to prove that BD = 2DC, I am super frustrated trying to solve this thing
@wraith hinge Has your question been resolved?
Yes
a hint would be to draw DM || EC where M is aa point on AB

