Question

using binomial theorem, find and simplify the coefficient near a^20 b^7 in the expression (a-b)^27

Answer 1

so first, what is the binomial theorem?

Answer 2

binomial coefficient would be \(n\choose k\), in this case \(n=27\) and \(k=7\) I suppose.

Answer 3

The subtle thing to remember is we have \((-b)^7\), so it becomes \(-b^7\).

Answer 4

so would it be a^20-(-7)*b??