Question

Find the product of $\sqrt{5}-2\sqrt{2}$ and its conjugate

• A. $-2$
• B. $3$
• C. $-3$
• D. $2$

Answer 1

The correct option is C $-3$

The conjugate of $\sqrt{5}-2\sqrt{2}$ is $\sqrt{5}+2\sqrt{2}$
$(\sqrt{5}-2\sqrt{2})(\sqrt{5}+2\sqrt{2})=5-4\times 2=-3$