Question

(3x-6)(3x+6)-3(2x-4)=?

Answer 1

$\displaystyle \tt (3x-6)(3x+6)-3(2x-4)=(3x)^2-6^2-3\cdot2x-3\cdot(-4)=\\\\ \displaystyle \tt =9x^2-36-6x+12=\bold{9x^2-6x-24}$