Question

If $x = \sqrt5 + 2$, find $x^2-4\sqrt5$.

• A. 1
• B. 7
• C. 9
• D. 3

Answer 1

Answer:

C. 9

Given:

$x=\sqrt5+2$

Find:

$x^2-4\sqrt5$

First calculate (x^2):

$(\sqrt5+2)^2$
$=5+4+4\sqrt5$
$=9+4\sqrt5$

Now,

$x^2-4\sqrt5$
$=(9+4\sqrt5)-4\sqrt5$
$=9$

So, the answer is:

$\boxed{9}$