~ Bạn tham khảo ~
`7, [x+2]/[x-1] + 3/[x+1] - [x^2]/[x^2-1]`
ĐKXĐ : `x\ne+-1`
`= [(x+2)(x+1)]/[(x+1)(x-1)] + [3(x-1)]/[(x+1)(x-1)] - [x^2]/[(x+1)(x-1)]`
`= [(x+2)(x+1)+3(x-1)-x^2]/[(x+1)(x-1)]`
`= [x^2+3x+2+3x-3-x^2]/[(x+1)(x-1)]`
`= [6x-1]/[(x+1)(x-1)]`
`8, [x+1]/[x-3] - 2/[x+3] - [4x]/[9-x^2]`
ĐKXĐ : `x\ne+-3`
`= [x+1]/[x-3] - 2/[x+3] + [4x]/[x^2-9]`
`= [(x+1)(x+3)]/[(x-3)(x+3)] - [2(x-3)]/[(x-3)(x+3)] + [4x]/[(x-3)(x+3)]`
`= [(x+1)(x+3)-2(x-3)+4x]/[(x-3)(x+3)]`
`= [x^2+4x+3-2x+6+4x]/[(x-3)(x+3)]`
`= [x^2+6x+9]/[(x-3)(x+3)]`
`= [(x+3)^2]/[(x-3)(x+3)]`
`= [x+3]/[x-3]`
