若x²+4x-4的值为0,则3x²+12x-5的值为?
问题描述:
若x²+4x-4的值为0,则3x²+12x-5的值为?
答
x²+4x-4=0
x^2=4-4x
3x²+12x-5
=3(4-4x)+12x-5
=12-12x+12x-5
=7