最佳回答取４０分：三條Simplify問題

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1. 2x/1-x + 2/x-1
= 2x / (1-x) - 2 / (1-x)
= (2x - 2) / (1-x)
= 2 (x - 1) / (1 - x)
= -2

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2. x+y/x-y - x-y/x+y
= [ ( x + y )^2 - ( x - y )^2 ] / ( x^2 - y^2 )
= [ ( x + y + x - y ) * ( x + y - x + y ) ] / ( x^2 - y^2 )
= 2x2y / ( x^2 - y^2 )
= 4xy / ( x^2 - y^2 )

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3. (2/a-3/5b) ÷ 2a-5b/12ab
= [ ( 10 b - 3 a ) / 5ab ] * ( 12 ab) / ( 2 a - 5 b )
= (120b - 36a) / (10a - 25b)

2x/1-x + 2/x -1
=2/(x-1) - -〔2x/(x-1)〕
=(2--2x)/(x-1)
=3x/(x-1)


x+y/x-y - x-y/x+y
=｛〔(x+y)(x-y)〕/ 〔(x^2)-(y^2)〕｝- ｛〔(x+y)(x-y)〕/ 〔(x^2)-(y^2)〕｝
= ｛〔(x^2)-(y^2)〕/〔(x^2)-(y^2)〕｝-｛〔(x^2)-(y^2)〕/〔(x^2)-(y^2)〕｝
= 1-1
= 0


(2/a-3/5b) ÷ 2a-5b/12ab
=〔(2/a)-(3/5b) 〕 × 12ab/(2a-5b)
= 〔(10b-3a)/5ab〕× 12ab/(2a-5b)
= 〔120a(b^2)-36(a^2)b〕/ 〔10(a^2)b-25a(b^2)〕

1.=x*
2=y
3=a÷ b