# How do you simplify sqrt(15x) times sqrt(21x)?

Jul 11, 2016

$3 x \sqrt{35}$

#### Explanation:

Notice that 3 is a factor of both 15 and 21 and so is $x$

$\sqrt{3 \times 5 \times x} \times \sqrt{3 \times 7 \times x}$

$\sqrt{3 x} \times \sqrt{5} \times \sqrt{3 x} \times \sqrt{7}$

But $\sqrt{3 x} \times \sqrt{3 x} = 3 x$

$3 x \sqrt{5} \sqrt{7} = 3 x \sqrt{5 \times 7} = 3 x \sqrt{35}$

$\sqrt{15 x} \cdot \sqrt{21 x} = 3 x \sqrt{35}$

#### Explanation:

$\sqrt{15 x} \cdot \sqrt{21 x}$

$\sqrt{\left(15 x\right) \cdot \left(21 x\right)}$

$\sqrt{\left(3\right) \left(5\right) x \cdot 3 \left(7\right) x}$

$\sqrt{{3}^{2} \cdot {x}^{2} \cdot 35}$

$3 x \sqrt{35}$

God bless....I hope the explanation is useful.