Question

Find the square of $\sqrt{5}-2$

• A. 9 - 4$\sqrt{5}$
• B. 9 - 4$\sqrt{3}$
• C. 9 - 5$\sqrt{5}$
• D. 5 - 4$\sqrt{5}$

Answer 1

The correct option is A

9 - 4$\sqrt{5}$

We use the basic subtraction identity for this.

We have$(\sqrt{5}-2{)}^2$ = $\sqrt{5}\sqrt{5}$ + 4 - 2 $\times$ 2$\sqrt{5}$

= 5 + 4 - 4$\sqrt{5}$

= 9 - 4$\sqrt{5}$