Question

Can someone help me solve this?
\[(2+\sqrt{5}) (6-2\sqrt{5})^{2}\]
Answer: a+b\sqrt{5}

Answer 1

okay

Answer 2

\[(2+\sqrt{5}) (6-2\sqrt{5})^{2}\]

Answer 3

Answer: \[a+b \sqrt{5}\]

Answer 4

first expand
\[ (6-2\sqrt{5})^2=... \]

Answer 5

I got \[-28+28\sqrt{5}\]
Did you get something else?

Answer 6

u must know this
\[\large (a-b)^2=a^2-2ab+b^2 \]

Answer 7

so
\[\large (6-2\sqrt{5})^2=6^2-2\times6\times2\sqrt{5}+[2\sqrt{5}]^2
=36-24\sqrt{5}+4\times5\]
\[\large =36-24\sqrt{5}+20=56-24\sqrt{5} \]

Answer 8

got it?

Answer 9

\[56-24\sqrt{5}\] That can't be the answer tho.. Thanks anyway :)

Answer 10

we haven't finished

Answer 11

so
\[\large (2+\sqrt{5})(6-2\sqrt{5})^2=(2+\sqrt{5})(56-24\sqrt{5})=... \]
can u do this?