Answer
$24 + 6 \sqrt 7$
Work Step by Step
Use the FOIL method to multiply the two binomials. With the FOIL method, we multiply the first terms first, then the outer terms, then the inner terms, and, finally, the last terms:
$=3(1) + 3(\sqrt 7) + (\sqrt{63}) + (\sqrt {63})(\sqrt 7)$
$=3 + 3\sqrt 7 + \sqrt {63} + \sqrt {441}$
Factor $\sqrt 63$ and $441$ so that one of the factors is a square of a number:
$=3 + 3(\sqrt 7) + \sqrt {(9)(7)} + (\sqrt {21(21)})\\
=3 + 3(\sqrt 7) + \sqrt {(3^2)(7)} + (\sqrt {21^2})$
Take out the square root of the perfect square number factors:
$=3 + 3\sqrt 7 + 3 \sqrt {7} + 21$
$=24 + 6 \sqrt 7$
