若x^2-4x+2=0,则3x^2-12x+7=_________?
问题描述:
若x^2-4x+2=0,则3x^2-12x+7=_________?
答
∵x^2-4x+2=0
∴x^2-4x=-2
两边同时乘以3
3x^2-12x=-6
则3x^2-12x+7
=-6+7
=1