解方程:(1)2x 2 +5x-3=0(配方法) &nbsp...

2025-04-06 07:15:08
推荐回答(1个)
回答1:

(1)x 2 +
5
2
x=
3
2

x 2 +
5
2
x+
25
16
=
3
2
+
25
16

(x+
5
4
)
2
=
49
16

x+
5
4
7
4

x=-
5
4
±
7
4

∴x 1 =3,x 2 =-
1
2


(2)3x 2 -5x-2=0,
a=3,b=-5,c=-2,
△=25+24=49,
x=
49
6
=
5±7
6

∴x 1 =2,x 2 =-
1
3


(3)2x(x-3)-5(x-3)=0,
(x-3)(2x-5)=0,
∴x-3=0,2x-5=0,
解得x 1 =3,x 2 =
5
2


(4)原方程整理得:
2x 2 -x-10=0,
(2x-5)(x+2)=0,
∴2x-5=0,x+2=0,
解得x 1 =
5
2
,x 2 =-2.