1计算:(a+b)÷(a方+ab)= 1/a
2当m= -1/2 时,等式x-1分之x=(x-1)(1-m)分之x(m+2)成立.
1-m=m+2
∴m=-1/2
3已知y分之x=3,则x方-xy分之2xy= 1
x/y=3
∴x=3y
∴x方-xy分之2xy=2y/(x-y)=2y/(3y-y)=1
4计算
(x-y)÷(x方-2xy+y方)
=(x-y)/(x-y)²
=1/(x-y)
(25-x方)÷(x方-10x+25)
=-(x+5)(x-5)/(x-5)²
=(x+5)/(5-x)
5已知a-b=0,求分式ab+b方分之x方-y方
这个题目似乎有点问题