Đáp án:
Giải thích các bước giải:
`a)`
`(sqrt6+sqrt{10})/(sqrt{21}+sqrt{35})`
`= (sqrt2(sqrt3+sqrt5))/(sqrt7(sqrt3+sqrt5))`
`= (sqrt2)/(sqrt7)`
`= (sqrt2sqrt7)/(sqrt7sqrt7)`
`= sqrt{14}/7`
`b)`
`(sqrt2+sqrt3+sqrt4-sqrt6-sqrt9-sqrt{12})/(sqrt2+sqrt3+sqrt4)`
`= (sqrt2+sqrt3+2-sqrt6-3-2sqrt3)/(sqrt2+sqrt3+2)`
`= (sqrt2-sqrt3-1-sqrt6)/(sqrt2+sqrt3+2)`
`= ((sqrt2-sqrt3-1-sqrt6)(sqrt2+sqrt3-2))/((sqrt2+sqrt3+2)(sqrt2+sqrt3-2))`
`= (2-2sqrt2-3+2sqrt3-sqrt2-sqrt3+2-2sqrt3-sqrt{18}+2sqrt6)/(2+2sqrt6+3-4)`
`= (1-6sqrt2-sqrt3+2sqrt6)/(1+2sqrt6)`
`= ((1-6sqrt2-sqrt3+2sqrt6)(1-2sqrt6))/((1+2sqrt6)(1-2sqrt6))`
`= (1-6sqrt2+24sqrt3-sqrt3+6sqrt2-24)/(1-24`
`= (-23+23sqrt3)/(-23)`
`= -(23(-1+sqrt3))/23`
`= -(-1+sqrt3)`
`= 1-sqrt3`
