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.

(1)x2+2x=5,
x2+2x+1=5+1,
(x+1)2=6,
x+1=±

6

x1=-1+
6
,x2=-1-
6

(2)2x2+7x-4=0,
(2x-1)(x-4)=0,
2x-1=0,x-4=0,
x1=
1
2
,x2=4.