What is the coefficient of xy in the expansion of (3x + (2y + 1))*(3x - (2y - 1))?
The coefficient of xy is -4.
This term would be
C(2,1)*(3x)^1 *(2y + 1)^1 =
2(3x)(2y + 1) =
6x(2y + 1) =
12xy + 6x
So....the coefficient is 12
