Question

先化简,后求值:2(x-3)(x+2)-(3+a)(3-a)其中a=-2,x=1

Answer 1

2(x-3)(x+2)-(3+a)(3-a)

=2x^2-2x-12-(9-a^2)

=2x^2-2x-12-9+-a^2

=2x^2-2x-21+a^2

=2x1x1-2x1-21+(-2)^2

=2-2-21+4

=-17