12mn-4m(m^2-3n+1)9（x+2)(x-2)-(3x-2)^2（x-3y+2）(x+3y+2)[(x+y)^2-(x-y)^2+4xy]/(-2x),其中x=-2 y=1/2解方程 2(2x-1)^2-8(x-1)(3+x)=34

前面那位后两题有误，来个修正版的
12mn-4m(m^2-3n+1)
=4m(3n-m²+3n-1)
=4m(-m²+6n-1)
=-4m(m²-6m+1)
9（x+2)(x-2)-(3x-2)^2
=9(x²-4)-9x²+12x-4
=9x²-36-9x²+12x-4
=12x-40
=4(3x-10)
（x-3y+2）(x+3y+2)
=(x+2-3y)(x+2+3y)
=(x+2)²-(3y)²
[(x+y)^2-(x-y)^2+4xy]/(-2x), 其中x=-2 y=1/2
原式=（4xy+4xy）/(-2x)
=8xy/(-2x)
=-4y 代入 y=1/2
=-2
2(2x-1)^2-8(x-1)(3+x)=34
8x²-8x+2-8x²-16x+24=34
-24x=8
x= --1/3

12mn-4m(m^2-3n+1)
=4m(3n-m²+3n-1)
=4m(-m²+6n-1)
=-4m(m²-6m+1)
9（x+2)(x-2)-(3x-2)^2
=9(x²-4)-9x²+12x-4
=9x²-36-9x²+12x-4
=12x-40
=4(3x-10)
（x-3y+2）(x+3y+2)
=(x+2-3y)(x+2+3y)
=(x+2)²-(3y)²
[(x+y)^2-(x-y)^2+4xy]/(-2x), 其中x=-2 y=1/2
原式=（x+y+x-y）(x+y-x+y)/(-2x)
=4xy/(-2x)
=-2y 代入 y=1/2
=-1
2(2x-1)^2-8(x-1)(3+x)=34
8x²-8x+2-8x²+16x-24=34
8x=34+22
8x=56
x=7

第一题：12mn-4m(m^2-3n+1) =12mn-4m^3+12mn-4m =-4m^3+24mn-4m =-4m(m^2-6mn+1)第二题：9（x+2)(x-2)-(3x-2)^2 =9(x^2-4)-(9x^2-12x+4) =9x^2-36-9x...

应该是这样解的。lz，祝你好好学习
12mn-4m(m^2-3n+1)
=4m(3n-m²+3n-1)
=4m(-m²+6n-1)
=-4m(m²-6m+1)
9（x+2)(x-2)-(3x-2)^2
=9(x²-4)-9x²+12x-4
=9x²-36-9x²+12x-4
=12x-40
=4(3x-10)
（x-3y+2）(x+3y+2)
=(x+2-3y)(x+2+3y)
=(x+2)²-(3y)²
[(x+y)^2-(x-y)^2+4xy]/(-2x), 其中x=-2 y=1/2
原式=（x+y+x-y）(x+y-x+y)/(-2x)
=4xy/(-2x)
=-2y 代入 y=1/2
=-1
2(2x-1)^2-8(x-1)(3+x)=34
8x²-8x+2-8x²+16x-24=34
8x=34+22
8x=56
x=7