1.x+2=x(x-2)
x^2-3x+2=0
(x-1)(x-2)=0
x=1 x=2
2.(x-3)^2-2(x-3)+1=0
[(x-3)-1]^2=0
x-4=0
x=4
3.(3x-4)^2=9x-12
(3x-4)^2=3(3x-4)
(3x-4）（3x-4-3)=0
（3x-4)（3x-7)=0
x=4/3 x=7/3
4.9(2x+3)^2-4(2x-5)^2=0
[3(2x+3)+2(2x-5)][3(2x+3)-2(2x-5)]=0
(10x-1)(2x+19)=0
x=1/10 x=-19/2
5.若整式 4x^2-2x-5与2x^+1互为相反数 求x的值
互为相反数想加等于0
于是有4x^2-2x-5+2x^2+1=0
6x^2-2x-4=0
3x^2-x-2=0
(3x+2)(x-1)=0
x=-2/3 x=1