若x²-3x+5=7则-2x²+6x+3=

问题描述:

若x²-3x+5=7则-2x²+6x+3=

x²-3x+5=7
x²-3x = 2
-2x²+6x+3=-2(x²-3x)+ 3 = -4 + 3 = -1