1.（m+n）^2-4m(m+n)+4m^2 分解因式
=(m+n-2m)²
=(n-m)²
2.(a-b)-2x(a-b)-x^2(b-a) 分解因式 去掉后面的平方
=（a-b)(1-2x+x²）
=（a-b)(1-x)²
3.(x^2+x-6)/(x-3)÷(x+3)/(x^2-6-x) 分式化简
=(x+3)(x-2)/(x-3)×(x-3)(x+2)/(x+3)
=(x-2)(x+2)
=x²-4
4.1/(x-3)-6/(x^2-9)-(x-1)/(6+2x) 分式化简
=1/(x-3)-6/(x+3)(x-3)-(x-1)/x(x+3)
=2(x+3)/2(x+3)(x-3)-12/2(x+3)(x-3)-2(x-1)(x-3)/2(x+3)(x-3)
=[2x+6-12-2(x-3)(x-1)]/2(x+3)(x-3)
=2(x-3)(1-x+1)/2(x+3)(x-3)
=-x/(2x+6)
5.[(x+2)/(x^2-2x)-(x-1)/(x^2-4x+4)]÷(4-x)/x 分式化简
=[(x+2)/x(x-2)-(x-1)/(x-2)²]×x/(4-x)
=(x²-4-x²+x)/x(x-2)²×x/(4-x)
=(x-4)/(x-2)²×1/(4-x)
=-1/(x²-4x+4)
6.(x+2)÷[x-(5x+4)/(1-x)] 其中x=1 先化简再求值
=(x+2)÷(x-x²-5x-4)/(1-x)
=(x+2)÷(x+2)²/(x-1)
=(x-1)/(x+2)
当x=1时
原式=0 注意这里x其实不能取1的
7.[x+1-15/(x-1)]÷(x-4) / (x-1) 其中x=（根号下3）-4 加了一个/
=（x²-1-15)/(x-1)÷(x-4)/(x-1)
=(x+4)(x-4)/(x-1)×(x-1)/(x-4)
=x+4
当x=√3-4时
原式=√3