`a)x^2/(x+1)+(2x)/(x^2-1)+1/(x+1)+1.đkxđ:xne+-1`
`=x^2/(x+1)+(2x)/((x-1)(x+1))+1/(x+1)+1`
`=(x^3-x^2+2x+x-1+x^2-1)/((x-1)(x+1))`
`=(x^3+3x-2)/(x^2-1)`
`b)(2xy)/(2x^2-xy)+(8y)/(y^2-4x^2)+(2x-y)/(2x^2+xy).đkxđ:xne0;xne+-y/2`
`=(2xy)/(x(2x-y))-(8y)/((2x-y)(2x+y))+(2x-y)/(x(2x+y))`
`=(2xy(2x+y)-8y+(2x-y)^2)/(x(2x+y)(2x-y))`
`=(2x^2y+2xy^2-8y+4x^2-4xy+y^2)/(x(2x+y)(2x-y))`
`c)1/(x-y)+(3xy)/(y^3-x^2)+(x-y)/(x^2+xy+y^2).đkxđ:xney`
`=(x^2+xy+y^2-3xy+x^2-2xy+y^2)/((x-y)(x^2+xy+y^2))`
`=(2x^2-4xy+2y^2)/((x-y)(x^2+xy+y^2))`
`=(2(x-y)^2)/((x-y)(x^2+xy+y^2))`
`=(2x-2y)/(x^2+xy+y^2)`
