Đáp án + Giải thích các bước giải:
`A=sqrt8-2sqrt18+3sqrt50`
`=2sqrt2-2*3sqrt2+3*5sqrt2`
`=2sqrt2-6sqrt2+15sqrt2`
`=(2-6+15)sqrt2=11sqrt2`
`B=sqrt125-10sqrt(1/20)-(sqrt5-5)/sqrt5`
`=5sqrt5-10/sqrt20-[sqrt5(sqrt5-5)]/5`
`=5sqrt5-10/(2sqrt5)-[sqrt5(1-sqrt5)]/(sqrt5)`
`=5sqrt5-5/(sqrt5)-(1-sqrt5)`
`=5sqrt5-sqrt5-1+sqrt5=5sqrt5-1`
`C=1/(sqrt5+sqrt2)+sqrt(7+4sqrt3)*sqrt2`
`=(sqrt5-sqrt2)/[(sqrt5-sqrt2)(sqrt5+sqrt2)]+sqrt(4+4sqrt3+3)*sqrt2`
`=(sqrt5-sqrt2)/(5-2)+sqrt(2^2+2*2*sqrt3+(sqrt3)^2]*sqrt2`
`=(sqrt5-sqrt2)/3+sqrt[(2+sqrt3)^2]*sqrt2`
`=(sqrt5-sqrt2)/3+|2+sqrt3|*sqrt2`
`=(sqrt5-sqrt2)/3+(2+sqrt3)*sqrt2`
`=(sqrt5-sqrt2)/3+[sqrt2(2+sqrt3)]`
`=(sqrt5-sqrt2)/3+[3*sqrt2(2+sqrt3)]/3`
`=(sqrt5-sqrt2)/3+(6sqrt2+3sqrt6)/3`
`=(sqrt5-sqrt2+6sqrt2+3sqrt6)/3=(sqrt5+5sqrt2+3sqrt6)/3`.
