(1)x²+6x+7=0 (2)x²-7x-8=0 (3)2x²+3=7x
问题描述:
(1)x²+6x+7=0 (2)x²-7x-8=0 (3)2x²+3=7x
用配方法解上列一元二次方程(详细一点,
答
1、X^2+6X=-7(X+3)^2=2X+3=±√2X1=-3+√2,X2=-3-√2,2、X^2-7X+(7/2)^2=8+(7/2)^2(X-7/2)^2=81/4X-7/2=±9/2X=7/2±9/2,X1=8,X2=-1,3、2X^2-7X=-3X^2-7/2X=-3/2,X^2-7/2X+(7/4)^2=-3/2+(7/4)^2,(X-7/4)^2=25/16X=7/...