Đáp án:
`A=-\sqrt{2}`
`B=1`
`C=1`
Giải thích các bước giải:
`A=\sqrt{18}-2\sqrt{50}+3\sqrt{8}`
`=\sqrt{3^2 . 2}-2\sqrt{5^2 .2}+3\sqrt{2^2 .2}`
`=3\sqrt{2}-2.5\sqrt{2}+3.2\sqrt{2}`
`=(3-10+6).\sqrt{2}=-\sqrt{2}`
Vậy `A=-\sqrt{2}`
$\\$
`B=\sqrt{27}-6\sqrt{1/3}+{\sqrt{3}-3}/\sqrt{3}`
`=\sqrt{3^2 .3}-\sqrt{{6^2}/3}+{\sqrt{3}.(1-\sqrt{3})}/\sqrt{3}`
`=3\sqrt{3}-\sqrt{12}+1-\sqrt{3}`
`=3\sqrt{3}-2\sqrt{3}+1-\sqrt{3}`
`=(3-2-1).\sqrt{3}+1=1`
Vậy `B=1`
$\\$
`C=5/{\sqrt{7}+\sqrt{2}}-\sqrt{8-2\sqrt{7}}+\sqrt{2}`
`={5(\sqrt{7}-\sqrt{2})}/{(\sqrt{7}+\sqrt{2})(\sqrt{7}-\sqrt{2})}-\sqrt{7-2\sqrt{7}.1+1^2}+\sqrt{2}`
`={5.(\sqrt{7}-\sqrt{2})}/{7-2}-\sqrt{(\sqrt{7}-1)^2}+\sqrt{2}`
`=\sqrt{7}-\sqrt{2}-(\sqrt{7}-1)+\sqrt{2}`
`=\sqrt{7}-\sqrt{2}-\sqrt{7}+1+\sqrt{2}=1`
Vậy $C=1$
