Question

can someone help me with a foil question

Answer 1

\[(3\sqrt{5}+\sqrt{3}) (\sqrt{5}-7\sqrt{3})\]

Answer 2

\[First:\; 3\sqrt{5} \times \sqrt{5} = 3 \sqrt{25} = 3 \times 5 = 15\]

Answer 3

\[Outer: \; 3\sqrt{5} \times (-7\sqrt{3}) = -21\sqrt{15}\]

Answer 4

\[Inner: \; \sqrt{3} \times \sqrt{5} = \sqrt{15}\]

Answer 5

\[Last: \; \sqrt{3} \times (-7\sqrt{3}) = -7\sqrt{9} = -7 \times 3 = -21\]

Answer 6

So all together
\[(3\sqrt{5} +\sqrt{3})(\sqrt{5} - 7\sqrt{3})\]
\[= 15 - 21\sqrt{15} + \sqrt{15} - 21\]
now gather like terms to finish.

Answer 7

-20\[-20\sqrt{15}-6\]

Answer 8

cool!