2 câu này là phần rút gọn

`color{#D0D0D0}{O}color{#C8C8C8}{m}color{#C0C0C0}{i}color{#B8B8B8}{s}color{#B0B0B0}{e}`

`11)`

Điều kiện xác định: `x ne +-1`

`(x/(2x-2)) + (3x/(2x+2)) - (2x^2/(x^2-1)) `

`= x/[2(x-1)] + 3x/[2(x+1)] - (2x^2)/((x-1)(x+1)) `

`= [x(x+1)]/[2(x-1)(x+1)] + [3x(x-1)]/[2(x-1)(x+1)] - [4x^2]/[2(x-1)(x+1)]`

`= [x(x+1) + 3x(x-1) - 4x^2] / [2(x-1)(x+1)] `

`= [x^2 + x + 3x^2 - 3x - 4x^2] / [2(x-1)(x+1)] `

`= [-2x] / [2(x-1)(x+1)]`

`= (-x )/ [(x-1)(x+1)]`

``

`12)`

Điều kiện xác định: `x ne +-1/2`

`(2x+1)/(4x-2) + (1-2x)/(4x+2) - (2/(1-4x^2)) `

`= (2x+1)/[2(2x-1)] + (1-2x)/[2(2x+1)] - 2/((1-2x)(1+2x)) `

`= (2x+1)/[2(2x-1)] + (1-2x)/[2(2x+1)] + 2/((2x-1)(2x+1))`

`= [(2x+1)(2x+1)]/[2(2x-1)(2x+1)] + [(1-2x)(2x-1)]/[2(2x-1)(2x+1)] + [4]/[2(2x-1)(2x+1)] `

`= [(2x+1)^2 + (1-2x)(2x-1) + 4] / [2(2x-1)(2x+1)] `

`= [(4x^2 + 4x + 1) + (2x - 1 - 4x^2 + 2x) + 4] / [2(2x-1)(2x+1)] `

`= [4x^2 + 4x + 1 + 4x - 4x^2 - 1 + 4] / [2(2x-1)(2x+1)] `

`= [8x + 4] / [2(2x-1)(2x+1)] `

`= [4(2x + 1)] / [2(2x-1)(2x+1)] `

`= 2 / (2x-1)`