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# C4 Binomial Expansion watch

1. Can anyone help with this question, much appreciated if u can:

The binomial expansion of (1+12x) ^(3/4) in ascending powers of x up to and including the term x³ is:

1+9x+px²+px³ |12x| < 1

a) find the value of p and the value of q

b) use this expansion with your values of p and q together with an appropriate value of x to obtain an estimate of (1.6)^(3/4)

c) obtain (1.6)^(3/4) from your calculator and hence make a comment on the accuracy of the estimate you obtained in part (b).
Can anyone help with this question, much appreciated if u can:

The binomial expansion of (1+12x) ^(3/4) in ascending powers of x up to and including the term x³ is:

1+9x+px²+px³ |12x| < 1

a) find the value of p and the value of q

b) use this expansion with your values of p and q together with an appropriate value of x to obtain an estimate of (1.6)^(3/4)

c) obtain (1.6)^(3/4) from your calculator and hence make a comment on the accuracy of the estimate you obtained in part (b).
a) 1 + 9x - 27x²/2 + 134x³/2

b) x= 0.05
we did this today for part three i think you have to use the formula - (your answer/real answer) x 100
i doubt it's necessary. you coould just say "ooh look, it's close", or if you're really clever "ooh look, it's correct to the nth decimal place"...
4. what formula are you guys on about?
5. (Original post by gordon2002)
what formula are you guys on about?
calculating percentage error
6. Erm in general:

n/r x 100, will give yo percentage difference where n is an approximation of r.

This isn't C4, it's GCSE percentages!

Hell it ain't even a formula, it's logic!
7. (Original post by Dekota)
Erm in general:

n/r x 100, will give yo percentage difference where n is an approximation of r.

This isn't C4, it's GCSE percentages!

Hell it ain't even a formula, it's logic!
think you're so clever do you dekota, huh?

well your post is incorrect. "n/r x 100, will give yo percentage difference where n is an approximation of r" won't give you the percentage difference, 1 - n/r x 100 will.

i'm just joking
8. (Original post by Dekota)

This isn't C4, it's GCSE percentages!

Hell it ain't even a formula, it's logic!
That's why I was confused about some fomula!

yeah, so basically value of x subbed into the expanded formula divided by actual times 100?
9. (Original post by chewwy)
think you're so clever do you dekota, huh?
Give me 1 and 1 and I can make 3.
i'm just joking
Haha, What goes around, comes around.
10. on a lighter note, that was my 2000th post. woohoo.
11. (Original post by chewwy)
on a lighter note, that was my 2000th post. woohoo.
A mathematical response: Technically, not really since there is a 0.75 chance that you've posted in the chat forum or welcome lounge, where posts don't count. So it is likely that you've past your 2000 posts mark ages ago!

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Updated: January 26, 2006
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