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Mats c2 help

The first three terms in ascending powers of x in the binomial expansion of (1 + px)12 are
given by
1 + 18x + qx2
where p and q are constants.
Find the value of p and the value of q.

Im confused ... :/
Reply 1
Use binomial theorem to find value of p - there can only be one value of p to give the coefficient of the x term to be 18. And from there you find q.
(1+px)12=1+(121)px+(122)(px)2++(px)12 (1+px)^{12} = 1+ \begin{pmatrix} 12 \\ 1 \end{pmatrix} px + \begin{pmatrix} 12 \\ 2 \end{pmatrix} (px)^2 +\cdots + (px)^{12} .
(edited 7 years ago)
Reply 2
Original post by B_9710
Use binomial theorem to find value of p - there can only be one value of p to give the coefficient of the x term to be 18. And from there you find q.
(1+px)12=1+(12c1)px+(12c2)(px)2++(px)12 (1+px)^{12} = 1+ (12\text{c}1)px + (12\text{c}2)(px)^2 +\cdots + (px)^12 .


So I used binomial expansion and got...... 1+12px+66p^2x^2 . Now what?
Reply 3
Original post by Starmock99
So I used binomial expansion and got...... 1+12px+66p^2x^2 . Now what?


What must 12p be equal to?

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