# Surds

• Nov 10th 2008, 01:57 AM
ni93
Surds
So I haven't had alot of time with my surds, and I'm basically stuck on the principals, I sorta see where I'm going but then somehow its all wrong (Worried)

I'll just show a few examples, then see if someone could explain it about (if you can =) )

2 /8 - 2 root 8

-2/18 + 6 - 6/2

-2 root 18 plus 6 - 6 root 2

/27 - /3 - 2/12

root 27 - root 3 - 2 root 12

Family has gone away the weekend, so no one I can really ask :S

Thanks you.
• Nov 10th 2008, 03:00 AM
vincisonfire
I don't know what you want to do but if it is to eliminate a root from the denominator you need to multiply by the conjugate.
EG $\frac{2}{8 - 2 \sqrt{ 8 }} = \frac{2}{8 - 2 \sqrt{ 8 }} \times \frac{8 + 2 \sqrt{ 8 }}{8 + 2 \sqrt{ 8 }}$

$\frac{16+4 \sqrt{8}}{64 - 16 \sqrt{ 8 }+ 16 \sqrt{ 8 } -32} =\frac{16+4 \sqrt{8}}{32}$

$\frac{4+ \sqrt{4\cdot 2}}{8}=\frac{4+ \sqrt{4}\sqrt{2}}{8}= \frac{4+ 2\sqrt{2}}{8}=\frac{2+ \sqrt{2}}{4}$