Đáp án+Giải thích các bước giải:
`j)(5+2sqrt5)/sqrt5-20/(5+sqrt5)-sqrt{20}`
`=(sqrt5(sqrt5+2))/sqrt5-(20(5-sqrt5))/(25-5)-sqrt{20}`
`=sqrt5+2-(20(5-sqrt5))/20-sqrt{4.5}`
`=sqrt5+2-5+sqrt5-2sqrt5`
`=-3`
`k)4/(sqrt3+1)-5/(sqrt3-2)+6/(sqrt3-3)`
`=4/(sqrt3+1)+5/(2-sqrt3)-6/(3-sqrt3)`
`=(4(sqrt3-1))/(3-1)+(5(2+sqrt3))/(4-3)-(6(3+sqrt3))/(9-3)`
`=(4(sqrt3-1))/2+(5(2+sqrt3))/1-(6(3+sqrt3))/6`
`=2sqrt3-2+10+5sqrt3-3-sqrt3`
`=5+6sqrt3`
`l)(15/(sqrt6+1)+4/(sqrt6-2)-12/(3-sqrt6))(sqrt{16}+11)`
`=((15(sqrt6-1))/(6-1)+(4(sqrt6+2))/(6-4)-(12(3+sqrt6))/(9-6))(4+11)`
`=((15(sqrt6-1))/5+(4(sqrt6+2))/2-(12(3+sqrt6))/3).15`
`=(3(sqrt6-1)+2(sqrt6+2)-4(3+sqrt6)).15`
`=15.(3sqrt6-3+2sqrt6+4-12-4sqrt6)`
`=15.(sqrt6-11)`
`=15sqrt6-165`
