请教几题..要详细过程!
1.(a^2/a-b)-a-b
=[a^2-(a+b)(a-b)]/(a-b)
=(b^2)/(a-b)
2.(1-(2/x+1))^2 /(x-1/x+1) ( 也就是1减x+1分之2的差的平方除以x+1分之x-1)
=[1-4/(x+1)^2-4/(x+1)]*[(x+1)/(x-1)]
=(x+1)/(x-1)-4/(x+1)(x-1)-4/(x-1)
=[(x+1)^2-4-4(x+1)]/(x+1)(x-1)
=[x^2-2x-7]/(x+1)(x-1)
3. 2ab/(a-b)(a+c) + 2bc/(a-b)(c-a)
=[2ab(c-a)+2bc(c+a)]/(a-b)(c+a)(c-a)
=[2b(2ac-a^2+c^2)]/(a-b)(c+a)(c-a)
4. (1/x-y + 1/x+y) 除以 xy/x^2-y^2
=[(x+y+x-y)/(x^2-y^2)]/[xy/x^2-y^2]
=2x/[x^2-y^2]*[x^2-y^2]/xy
=2/y