# Thread: Simplifying Surd

1. ## Simplifying Surd

Hi

Ive just solved a quadratic equation using the quadratic formula, but the qestion says to leave it in the form a(+ or -) root b.

I got the answer (2(+ or -) root 84) / 2

How can i change this to the required form? I know i can divide the 2 by 2 leaving 1 (+ or -) (root 84)/2. Not sure about the root.

By the way sorry about the layout of the equation. I still havn't got the hang of the math code. Hopefully you still understand what i mean.

2. Originally Posted by nugiboy
Hi

Ive just solved a quadratic equation using the quadratic formula, but the qestion says to leave it in the form a(+ or -) root b.

I got the answer (2(+ or -) root 84) / 2

How can i change this to the required form? I know i can divide the 2 by 2 leaving 1 (+ or -) (root 84)/2. Not sure about the root.

By the way sorry about the layout of the equation. I still havn't got the hang of the math code. Hopefully you still understand what i mean.
$\sqrt{84} = \sqrt{4 \cdot 21}= 2\sqrt{21}$
Can you solve it now?