Question

(8+√5)(8-√5)

A. 59-16√5
B. 64-18√5
C. 59
D.69

Answer 1

Your have :
\[(8+\sqrt{5})(8-\sqrt{5}) = 8\times8 - 8 \times \sqrt{5} + 8 \times \sqrt{5} - \sqrt{5} \times \sqrt{5}\]
I just multiply 8 with
N\[(8-\sqrt{5})\]
and
\[\sqrt{5}\]
with

\[(8-\sqrt{5})\]
now it's to you to complete.

Answer 2

?

Answer 3

\[8\times8 - 8\sqrt{5} + 8\sqrt{5} - \sqrt{5}\sqrt{5}\] =
\[64 - 8\sqrt{5} + 8\sqrt{5} - \sqrt{5}\sqrt{5}\] = ?