I understand Binomial Theorem, but this was an extension question and I can't find the answer.

Quote:

In the expansion of (1+bx)^n , the first three terms are 1-3x+(15/4)x^2. Find b and n.

Could someone please help me? Thanks.

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- May 4th 2012, 12:20 PMmcshineBinomial Theorem
I understand Binomial Theorem, but this was an extension question and I can't find the answer.

Quote:

In the expansion of (1+bx)^n , the first three terms are 1-3x+(15/4)x^2. Find b and n.

Could someone please help me? Thanks.

- May 4th 2012, 12:29 PMMathoManRe: Binomial Theorem
$\displaystyle (a+b)^n=\sum\limits_{k=0}^n {n \choose k}a^{n-k}b^k$.

So the first three terms are: $\displaystyle {n\choose 0}a^nb^0 +{n \choose 1}a^{n-1}b^1+{n \choose 2}a^{n-2}b^2$.

Take it from there... - May 4th 2012, 12:30 PMa tutorRe: Binomial Theorem
Write out the first three terms of the expansion and compare it to 1-3x+15x^2/4.