câu 1; (3√8 - 4√2 + √40 ) √2 - √180 câu 2 ; √20 + √125 - √80 câu 3 ; 3√72 + √200 + 9√2 - 5√50 câu 4; 3√3+ 4√12 - 5√27

`y10000`

`1)` `(3\sqrt{8}-4\sqrt{2}+\sqrt{40})``\sqrt{2}` `-` `\sqrt{180}`

`=` `(6\sqrt{2}-4\sqrt{2}+\sqrt{40})``\sqrt{2}` `-` `\sqrt{180}`

`=` `(2\sqrt{2}+2\sqrt{10})``\sqrt{2}` `-` `\sqrt{180}`

`=` `2(\sqrt{2})^2` `+` `2\sqrt{10}``\sqrt{2}` `-` `\sqrt{180}`

`=` `4` `+` `2\sqrt{20}``-` `6\sqrt{5}`

`=` `4` `+` `4\sqrt{5}` `-` `6\sqrt{5}`

`=` `4` `-` `2\sqrt{5}`

`2)` `\sqrt{20}` `+` `\sqrt{125}` `-` `\sqrt{80}`

`=` `2\sqrt{5}` `+` `5\sqrt{5}` `-` `4\sqrt{5}`

`=` `(2+5-4)` `\sqrt{5}`

`=` `3` `\sqrt{5}`

`3)` `3\sqrt{3}``+` `4\sqrt{12}` `-` `5\sqrt{27}`

`=` `3\sqrt{3}``+` `8\sqrt{3}` `-` `15\sqrt{3}`

`=` `(3+8-15)` `\sqrt{3}`

`=` `-` `4` `\sqrt{3}`