Math Help - pls tell me how to do this :(

1. please tell me how to do this :(

express (2+sqrt3)(5-2sqrt3) in the form a+bsqrtc.

can someone teach me how to get it ?

2. Originally Posted by charl0tte
express (2+sqrt3)(5-2sqrt3) in the form a+bsqrtc.

can someone teach me how to get it ?
To express $(2+\sqrt 3)(5-2\sqrt 3)$ in the form $a+b\sqrt c$ begin by multiplying out the brackets:

$
(2+\sqrt 3)(5-2\sqrt 3)=2(5-2\sqrt 3)+\sqrt 3 (5-2\sqrt 3)
$
$
=10-4\sqrt 3 + \sqrt 3 (5-2\sqrt 3)
$

$
=10-4\sqrt 3 + 5\sqrt 3-2\sqrt 3 \sqrt 3
$

$
=10-4\sqrt 3 + 5\sqrt 3-6
$

$
=4+\sqrt 3
$

RonL

3. thx !!