binomial expansion pure year 2

[whole otter]

How can I do part b of question 6?

And also part C

[terse jay]

on it

[whole otter]

Thanks

I’ve looked at the mark scheme but I just don’t understand the part B and C

[terse jay]

What exercise is this

[whole otter]

Exercise 4

Mixed exercises

Question 6

Year 2 pure

[wary shore]

yo so

[whole otter]

Just need help on part C now I done part b

[wary shore]

oh ok so

finding a value for x

so what do you know about what x can be#

does x have any restrictions

[whole otter]

Below 1/3

Mod

[wary shore]

yeah so

[whole otter]

They sub in 0.01 in the mark scheme idk why tho

[wary shore]

what we can do is guess a bit

try get something that matches a bit

[wary shore]

Like if the top is 101 and we have 1+x

We want smth that looks like 1.01 or smth right

[whole otter]

Yh

[wary shore]

Yeah so they just spot that 0.01 works

To actually like deduce it

You can just set the fraction equal to your 1+x / 1+3x

And try solve

So 101/103 = (1+x)/(1+3x)

That’s how to get it every time but as you can see it’s a bit of algebra work

[whole otter]

So they just picked it from common sense, I see

And trying it

[wary shore]

Yeah

[whole otter]

Yeah got it now, thanks

[wary shore]

Nws