Question

a/b=-2,求(a^2-2ab-3b^2)/(a^2-6ab-7b^2)的值,快!

Answer 1

a=-2b

(a^2-2ab-3b^2)/(a^2-6ab-7b^2)

=(a-3b)(a+b)/[(a-7b)(a+b)

=(a-3b)/(a-7b)

=(-2b-3b)/(-2b-7b)

=-5b/(-9b)

=5/9