计算：(a/a+b - b/b-a - 2ab/a^2-b^2)÷(1/a-1/b) 解方程：5/x+1 - 4/x =0 2-x/x-3 =1- 1/3-x 5/x-1=3/x5/x+1 - 4/x =02-x/x-3 =1- 1/3-x 5/x-1=3/x+1
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计算：(a/a+b - b/b-a - 2ab/a^2-b^2)÷(1/a-1/b) 解方程：5/x+1 - 4/x =0 2-x/x-3 =1- 1/3-x 5/x-1=3/x5/x+1 - 4/x =02-x/x-3 =1- 1/3-x 5/x-1=3/x+1
计算：(a/a+b - b/b-a - 2ab/a^2-b^2)÷(1/a-1/b) 解方程：5/x+1 - 4/x =0 2-x/x-3 =1- 1/3-x 5/x-1=3/x
5/x+1 - 4/x =0
2-x/x-3 =1- 1/3-x
5/x-1=3/x+1
计算：(a/a+b - b/b-a - 2ab/a^2-b^2)÷(1/a-1/b) 解方程：5/x+1 - 4/x =0 2-x/x-3 =1- 1/3-x 5/x-1=3/x5/x+1 - 4/x =02-x/x-3 =1- 1/3-x 5/x-1=3/x+1
(a/a+b - b/b-a - 2ab/a^2-b^2)÷(1/a-1/b)
=[a*(a-b)+b*(a+b)-2ab)]/[(a+b)(a-b)]*(ab)/(b-a)
=(a-b)/(a+b)*(ab)/(b-a)
=-ab/(a+b)
5/(x+1) - 4/x =0
(5x-4x-4)/[x(x+1)]=0
x=4 代入x(x+1)＝20≠0 成立
(2-x)/(x-3) =1- 1/(3-x)
两边同乘x-3
2-x=x-3+1
x=2 代入x -3＝-1≠0 成立
5/(x-1)=3/(x+1)
两边同乘(x-1)(x+1)
5x+5=3x-3
2x=-8
x=-4 代入(x-1)(x+1)＝15≠0 成立
(a/a+b - b/b-a - 2ab/a^2-b^2)÷(1/a-1/b) =[a(a-b)+b(a+b)-2ab]/(a^2-b^2)÷(1/a-1/b)
=(a-b)^2/[(a+b)(a-b)]÷(-a+b)/ab=-ab/(a+b)
(1) (a/a+b - b/b-a - 2ab/a^2-b^2)÷(1/a-1/b) =[a(a-b)+b(a+b)-2ab/(a^2-b^2)]÷[(b-a)/ab]
=[（a^2-2ab+b^2)/(a^2-b^2)]*[-ab/(a-b)]=(a-b)/(a+b)*[-ab/(a-b)]=-ab/(a+b)
(2)本小问是否有问题，方程不可能出现多个等号，除非是解方程组