# Simplifying Surd

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• Jan 8th 2008, 02:07 AM
nugiboy
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.
• Jan 8th 2008, 02:52 AM
Isomorphism
Quote:

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.

$\displaystyle \sqrt{84} = \sqrt{4 \cdot 21}= 2\sqrt{21}$
Can you solve it now?