Question

Simplfy
$\sqrt{20} \times \sqrt{3} \times \sqrt{18}$
A
$5 \sqrt{30}$
B
$5 \sqrt{10}$
C
$6 \sqrt{30}$
D
$6 \sqrt{10}$
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Simplify
$5 \sqrt{7} + \sqrt{7} - 2 \sqrt{7}$
A
$4 \sqrt{21}$
B
$3 \sqrt{21}$
C
$4 \sqrt{7}$
D
$3 \sqrt{7}$



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Answer 1

Answer:

$\large\boxed{C.\ 6\sqrt{30}}\\\boxed{C.\ 4\sqrt7}$

Step-by-step explanation:

$\text{Use}\ \sqrt{ab}=\sqrt{a}\cdot\sqrt{b} \\\\\sqrt{20} \times \sqrt{3} \times \sqrt{18}=\sqrt{20\times3\times18}=\sqrt{4\times5\times3\times3\times6}\\\\=\sqrt4\times\sqrt9\times\sqrt{5\times6}=2\times3\times\sqrt{30}=\boxed{6\sqrt{30}}\\==============================\\\\5 \sqrt{7} + \sqrt{7} - 2 \sqrt{7}=5 \sqrt{7} + 1\sqrt{7} - 2 \sqrt{7}=(5+1-2)\sqrt7=\boxed{4\sqrt7}$