`b)` `frac{2}{2x+1}-frac{1}{2x-1}+frac{2}{4x^2-1}`
Điều kiện xác định: `x\ne±1/2`
`=frac{2(2x-1)}{(2x-1)(2x+1)}-frac{2x+1}{(2x-1)(2x+1)}+frac{2}{(2x-1)(2x+1)}`
`=frac{2(2x-1)-(2x+1)+2}{(2x-1)(2x+1)}`
`=frac{4x-2-2x-1+2}{(2x-1)(2x+1)}`
`=frac{2x-1}{(2x-1)(2x+1)}`
`=frac{1}{2x+1}`