(1)2x2-7x+5=0,
b2-4ac=(-7)2-4×2×5=9,
x=
,7±
9
2×2
x1=1,x2=
.5 2
(2)3x2-10x-5=0,
3x2-10x=5,
x2-
x=10 3
,5 3
配方得:x2-
x+(10 3
)2=5 3
+(5 3
)2,5 3
(x-
)2=5 3
,40 9
开方得:x-
=±5 3
,2
10
3
x1=
,x2=5+2
10
3
.5?2
10
3
(3)2x(x-3)=9-3x,
2x(x-3)+3(x-9)=0,
(x-3)(2x+3)=0,
x-3=0,2x+3=0,
x1=3,x2=-
.3 2
(4)(x-5)(x+2)=8,
x2-3x-18=0,
(x-6)(x+3)=0,
x-6=0,x+3=0,
x1=6,x2=-3.