Question

Tìm x A. X.(x+1)-x-1=0 B.2x(x-1)²-2x(x+1)²=0 C. 2x(x-2)+x(x+5)=0

Answer 1

`a)x(x+1)-x-1=0`

`<=>x(x+1)-(x+1)=0`

`<=>(x+1)(x-1)=0`

`<=>x^2-1=0`

`<=>x^2=1<=>x=+-1`

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`b)2x(x-1)^2-2x(x+1)^2=0`

`<=>2x[(x-1)^2-(x+1)^2]=0`

`<=>2x(x-1-x-1)(x-1+x+1)=0`

`<=>2x.2x=0`

`<=>x=0`

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`c)2x(x-2)+x(x+5)=0`

`<=>x[2(x-2)+x+5]=0`

`<=>x(2x-4+x+5)=0`

`<=>x(3x+1)=0`

`<=>[(x=0),(x=-1/3):}`