a)can20+can80-can45 b) can98-can72+0,5can8 c)(can28-2can14+can7)*can7+7can8
2 câu trả lời
$A)$ $\sqrt{20}+\sqrt{80}-\sqrt{45}$
$=2\sqrt{5}+4\sqrt{5}-3\sqrt{5}$
$=3\sqrt{5}$
_______________________
$B)$ $\sqrt{98}-\sqrt{72}+0,\:5\sqrt{8}$
$=7\sqrt{2}-6\sqrt{2}+\sqrt{2}$
$=2\sqrt{2}$
_______________________
$C)$ $\left(28-2\sqrt{14}+\sqrt{7}\right).\sqrt{7}+7\sqrt{8}$
$=28\sqrt{7}-14\sqrt{2}+7+14\sqrt{2}$
$=28\sqrt{7}+7$
`a)sqrt20+sqrt80-sqrt45`
`=2sqrt5+4sqrt5-3sqrt5`
`=3sqrt5`
`b)sqrt98-sqrt72+0,5sqrt8`
`=7sqrt2-6sqrt2+sqrt2`
`=2sqrt2`
`c)(sqrt28-2sqrt14+sqrt7).sqrt7+7sqrt8`
`=14-14sqrt2+7+14sqrt2`
`=21`
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