Đáp án:
`a, 2√50 - 3√2 +1/3 √18`
`= 2.(√25 . √2)- 3√2 +1/3 .(√9.√2)`
`= 2.5√2-3√2+1/3. 3√2`
`= 10√2-3√2+√2`
`= √2(10-3+1)`
`= 8√2`
`b, (√10-√5)/(√2-1)-(√21-√7)/(1-√3)-5/(√5)`
`= (√5 . √2 -√5)/(√2-1)+(√7.√3-√7)/(√3-1)-((√5)^2)/(√5)`
`= (√5(√2-1))/(√2-1)+(√7(√3-1))/(√3-1)-√5`
`= √5+√7-√5`
`= √7`
c, $\sqrt[]{7-4√3}$
= $\sqrt[]{4-4√3+3}$
= $\sqrt[]{2^2-2.2.√3+(√3)^2}$
= $\sqrt[]{(2-√3)^2}$
`= |2-√3|`
`= 2-√3`
