Question

One more binomial expansion problem.

Answer 1

The second image is my work so far, I'm not sure how to find the value of 'a'

Answer 2

\(\large\tt \begin{align} \color{black}{(2x+3)^0=1~~term\\~\\
(2x+3)^1=2~~terms\\~\\
(2x+3)^2=3~~terms\\~\\
.\\~\\
.\\~\\
.\\~\\
.\\~\\

(2x+3)^{17}=18~~terms\\~\\
(2x+3)^{2a-5}=18~~terms----(given)\\~\\
(2x+3)^{2a-5}=(2x+3)^{17}\\~\\~\\
\Large 2a-5=17\\~\\
\Large a=11
}\end{align}\)

Answer 3

ah, well put! Thank you very much! :D