Question

Expanding binomials unit, solve for a?

Answer 1

\[6a=252?\]

Answer 2

\[a=42\]

Answer 3

By the binomial theorem, you have
\[(ax-y)^6=\sum_{k=0}^6\binom{6}{k}(ax)^ky^{6-k}\]
The given term, \(-252xy^5\), occurs for \(k=1\) (check the power on \(y\)).
\[\binom61(ax)^1y^{6-1}=6axy^5=-252xy^5~~\implies~~6a=-252\]

Answer 4

Thanks @SithsAndGiggles I got the same result! :)