分式的约分18(b-a)2(2是指平方）/24(a-b)如何变成3(a-b)/4?(x+y)2(指平方)-10(x+y)

18(b-a)2(2是指平方）/24(a-b)如何变成3(a-b)/4?
(b-a)^2=(a-b)^2
所以18(b-a)^2/[24(a-b)]=3(a-b)/4
分子分母同去6(a-b)
[(x+y)^2-10(x+y)+25]/[(x+y)^2-25]
=(x+y-5)^2/[(x+y+5)(x+y-5)]
=(x+y+5)/(x+y-5)