Question

Multiply. Simplify if possible. Is my answer to the following problem correct?

(sqrt7 -sqrt8)(sqrt7 +sqrt8)

is the answer -14+sqrt(8)8?

Answer 1

\[(\sqrt7 -\sqrt8)(\sqrt7 +\sqrt8)\]

Answer 2

7-8=-1 is the answer

Answer 3

wow! I was waaaay off. lol

Answer 4

you are using
\[(a+b)(a-b)=a^2-b^2\]

Answer 5

Use the idea that \[(A-B)(A+B)=A^2-B^2\] to get \[(\sqrt{7}-\sqrt{8})(\sqrt{7}+\sqrt{8})=(\sqrt{7})^2-(\sqrt{8})^2=7-8=-1\]

Answer 6

Just multiply them or use the formula \[a ^{2}-b ^{2}=(a+b)(a-b)\]

Answer 7

so the answer is -1 or 7? I'm confused again lol

Answer 8

-1 never mind :)

Answer 9

so if I did \[(\sqrt2)(-2\sqrt2 +3)\]
the answer is not 3sqrt 2-4 is it?

Answer 10

\[\sqrt{2}(-2\sqrt{2}+3)\]


\[-2\sqrt{2}*\sqrt{2}+3\sqrt{2}\]


\[-2\sqrt{2*2}+3\sqrt{2}\]


\[-2\sqrt{4}+3\sqrt{2}\]


\[-2*2+3\sqrt{2}\]


\[-4+3\sqrt{2}\]


\[3\sqrt{2}-4\]


So you got it.

Answer 11

awesome!