已知4x^2+7x-1=3,求-12x^2-21x

问题描述:

已知4x^2+7x-1=3,求-12x^2-21x

4x^2+7x-1=3
4x^2+7x=4
-12x^2-21x
=-3(4x^2+7x)
=-3*4
=-12