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# Unsure on how to answer these questions (binomial expansion c4) Watch

1. The questions in particular are 3 and 6
Im not sure how you solve these as normally
The expansion isn't multiplied by another value . I had thought i needed to multiply first or multiply the end result by whats before it however im not getting any right answers.

How exactly do you solve these questions
To note I can do something like
First few terms of 7x+12/(x+3)(x+4) or (1+x/4)^1/2
But not
(x+1)(1+x/4)^1/2
What exactly do you need to do ?
2. Expand and then multiply.
3. (Original post by Vanetti)

The questions in particular are 3 and 6
Im not sure how you solve these as normally
The expansion isn't multiplied by another value . I had thought i needed to multiply first or multiply the end result by whats before it however im not getting any right answers.

How exactly do you solve these questions
To note I can do something like
First few terms of 7x+12/(x+3)(x+4) or (1+x/4)^1/2
But not
(x+1)(1+x/4)^1/2
What exactly do you need to do ?
Have you got any working out to show? Because I would work out the binomial expansion then multiply by (1+x) for question 3 but you said that you dont get the correct answer?

Posted from TSR Mobile
4. (Original post by Vanetti)

The questions in particular are 3 and 6
Im not sure how you solve these as normally
The expansion isn't multiplied by another value . I had thought i needed to multiply first or multiply the end result by whats before it however im not getting any right answers.

How exactly do you solve these questions
To note I can do something like
First few terms of 7x+12/(x+3)(x+4) or (1+x/4)^1/2
But not
(x+1)(1+x/4)^1/2
What exactly do you need to do ?
(x+1)(1+x/4)^1/2 = (x+1)(1 + x/8 - x^2/128 + x^3/1024 - ...) using the binomial expansion,
and now multiply out as x + x^2/8 - x^3/128 + x^4/1024 - ... + 1 + x/8 - x^2/128 + x^3/1024 - ...
= 1 + 9x/8 + 15x^2/128 - 7x^3/1024 + ...
5. (Original post by HFancy1997)
Have you got any working out to show? Because I would work out the binomial expansion then multiply by (1+x) for question 3 but you said that you dont get the correct answer?

Posted from TSR Mobile
Turns out I did have the correct answer but had an extra
-4x^4 which I didn't realize the question had said in ascending powers of x (so that value isn't needed) thanks for the help I had thought I needed some random method or something

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