# How do you evaluate 2\sqrt { 15} ( 3+ \sqrt { 5} )?

$2 \sqrt{15} \left(3 + \sqrt{5}\right) = 6 \sqrt{15} + 2 \sqrt{75}$
$= 6 \sqrt{5 \setminus \times 3} + 2 \sqrt{25 \setminus \times 3}$
$= 6 \sqrt{5} \sqrt{3} + 10 \sqrt{3}$
$= \sqrt{3} \left(6 \sqrt{5} + 10\right)$
Now substitute values for $\sqrt{5}$ and $\sqrt{3}$.
$= 1.732 \left(6 \setminus \times 2.236 + 10\right)$
$= 1.732 \setminus \times 23.416$
$= 40.556$ upto 3rd decimal precision