Đáp án:
Giải thích các bước giải:
$\sqrt{18}$`-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`$\sqrt{2}$
`= `$\sqrt{2}$ `( 3 -10 +6)`
` =-`$\sqrt{2}$
c)
$\sqrt{8-2\sqrt{7}}$`-`$\sqrt{11+4\sqrt{7}}$
`= `$\sqrt{7 -2.\sqrt{7}.1 + 1^2}$ `- `$\sqrt{7 + 2.\sqrt{7}.2 +2 ^2}$
`=` $\sqrt{(\sqrt{7}-1)^2}$ `-` $\sqrt{(\sqrt{7}+2)^2}$
` =` |$\sqrt{7}$`-1| -|`$\sqrt{7}$`+2|`
`=` $\sqrt{7}$ `-1 -(`$\sqrt{7}$`+2)`
`=`$\sqrt{7}$`-`$\sqrt{7}$`- 2-1`
`=-3`
