解方程:(1)x2+2x=5; (2)2x2+7x-4=0.
问题描述:
解方程:
(1)x2+2x=5;
(2)2x2+7x-4=0.
答
(1)x2+2x=5,
x2+2x+1=5+1,
(x+1)2=6,
x+1=±
,
6
x1=-1+
,x2=-1-
6
;
6
(2)2x2+7x-4=0,
(2x-1)(x-4)=0,
2x-1=0,x-4=0,
x1=
,x2=4.1 2