C Clifford Junior Member Joined Nov 15, 2006 Messages 81 Mar 31, 2007 #1 Given (1 + ay)^n, the first three terms are 1, 12y and 68y^2 respectively. Solve for a and n. I have absolutely no idea where to begin this question. Can somebody put me on the right track?
Given (1 + ay)^n, the first three terms are 1, 12y and 68y^2 respectively. Solve for a and n. I have absolutely no idea where to begin this question. Can somebody put me on the right track?
pka Elite Member Joined Jan 29, 2005 Messages 11,978 Mar 31, 2007 #2 \(\displaystyle \L \left( {x + y} \right)^n = \sum\limits_{k = 0}^n {\left( {\begin{array}{c} n \\ k \\ \end{array}} \right)x^{n - k} y^k } = x^n + nx^{n - 1} y + \frac{{n\left( {n - 1} \right)}}{2}x^{n - 2} y^2 \cdots\)
\(\displaystyle \L \left( {x + y} \right)^n = \sum\limits_{k = 0}^n {\left( {\begin{array}{c} n \\ k \\ \end{array}} \right)x^{n - k} y^k } = x^n + nx^{n - 1} y + \frac{{n\left( {n - 1} \right)}}{2}x^{n - 2} y^2 \cdots\)
