Đáp án:
`d)(sqrt6+sqrt{15})/(sqrt{14}+sqrt{35})`
`=(sqrt3(sqrt2+sqrt5))/(sqrt7(sqrt2+sqrt5))`
`=sqrt3/sqrt7`
`=sqrt{21}/7`
`e)(x-4sqrtx+4)/(x-4)(x>=0,x ne 4)`
`=(sqrtx-2)^2/((sqrtx-2)(sqrtx+2))`
`=(sqrtx-2)/(sqrtx+2)`
`g)G=3/(x^2-y^2)*sqrt{(16(x^2+2xy+y^2))/9}(x ne +-y)`
`=3/((x-y)(x+y))*sqrt{(16(x+y)^2)/9}`
`=3/((x-y)(x+y))*4/3|x+y|`
Nếu `x> -y=>x+y>0`
`=>G=3/((x-y)(x+y))*4/3(x+y)`
`G=4/(x-y)`
Nếu `x<-y=>x+y<0`
`=>G=3/((x-y)(x+y))*(-4)/3(x+y)`
`G=-4/(x-y)`
