`(x+3)/(x+1) +(2x-1)/(x-1) +(x+5)/(x^2 -1)`
`= ((x+3)(x-1))/((x+1)(x-1)) + ((2x-1)(x+1))/((x-1)(x+1)) + (x+5)/((x-1)(x+1))`
`= (x^2 +3x-x-3)/((x+1)(x-1))+(2x^2 -x+2x-1)/((x+1)(x-1))+(x+5)/((x+1)(x-1))`
`=(x^2 +3x-x-3+2x^2 -x+2x-1+x+5)/((x+1)(x-1))`
`= (3x^2 +4x+1)/((x+1)(x-1))`
`=(3x^2 +3x+x+1)/((x+1)(x-1))`
`= (3x(x+1)+(x+1))/((x+1)(x-1))`
`=((x+1)(3x+1))/((x+1)(x-1))`
`=(3x+1)/(x-1)`
Xin ctlhn cho nhóm
