Asked by Harry

If (1+px)^n = 1 + 15x +90x^2 +... , find the values of p and n.

Answer: p=3, n=5
Thanks for any help
Answered by R_scott
expanding the binomial ... (1 + px)^n = nC0 1^n + nC1 1^(n-1) (px)^1 +
nC2 1^(n-2) (px)^2 + ...

2nd term ... n p = 15

3rd term ... [n (n - 1) / 2] p^2 = 90

dividing terms ... (n - 1) p = 12 ... n p - p = 12

subtracting equations ... p = 3

substitute back to find n
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