八下数学，分式约分和通分

1:原式=a(a-b)/(a+b)(a-b)=a/(a+b)
2:原式=(3a+2b)(3a-2b)/(3a-2b)^2=(3a+2b)/(3a-2b)
3:左式=5/(x+1)(x-1),右式=x/(x-1)^2,两式通分
左式=5(x-1)/(x^3-x^2-x+1),右式=(x^2+x)/(x^3-x^2-x+1)
4:通分左式=2xy(x-y)/(x+y)^2(x-y)=(2x^2y-2xy^2)/(x^3+x^2y-xy^2-y^3)
右式=x(x+y)/(x+y)(x^2-y^2)=(x^2+xy)/(x^3+x^2y-xy^2-y^3)

(1)原式=a(a-b)/[(a-b)(a+b)]=a/(a+b)
(2)原式=(3a-2b)(3a+2b)/(3a-2b)^2=(3a+2b)/(3a-2b)
(3)原式=5/[(x-1)(x+1)] 和x/(x-1)^2 最简分母:[(x-1)^2(x+1)]
所以5(x-1)/[(x-1)^2(x+1)]和x(x+1)/[(x-1)^2(x+1)]
(4)原式=2xy(x-y)/[(x+y)^2(x-y)]和x(x+y)/[(x+y)^2(x-y)] 最简分母:[(x+y)^2(x-y)]

(1)(a^2-ab)/(a^2-b^2)=a(a-b)/(a+b)(a-b)=a/(a+b)

(2)(9a^2-4b^2)/(9a^2-12ab+4b^2)=(3a+2b)(3a-2b)/(3a-2b)^2=(3a+2b)/(3a-2b)

(3)5/(x^2-1)=5/(x+1)(x-1)=5(x-1)/(x+1)(x-1)^2
x/(x^2-2x+1)=x/(x-1)^2=x(x+1)/(x+1)(x-1)^2

(4)2xy/(x+y)^2=2xy(x-y)/(x-y)(x+y)^2
x/(x^2-y^2)=x/(x+y)(x-y)=x(x+y)/(x-y)(x+y)^2

1.(a+b)分之a
2.（3a-2b)分之(3a+2b)
3.最简公分母：（X-1)的平方乘（X+1） 所以：<