# conjugate

• Feb 16th 2009, 12:57 AM
salam
conjugate

2√3
√5+2 √6

buh i need help again...:(
• Feb 16th 2009, 01:02 AM
Jameson
$\frac{2\sqrt{3}}{\sqrt{5}+2\sqrt{6}}$

The conjugate of a+b is simply a-b. What's nice about this product is you will get a^2-b^2, which eliminates square roots. Multiply the numerator and denominator by the conjugate of the denominator.
• Feb 16th 2009, 01:18 AM
salam
could u please show me the working to it
so, express with rational denominator
thanks
• Feb 16th 2009, 02:06 AM
Jameson
Quote:

Originally Posted by salam
could u please show me the working to it
so, express with rational denominator
thanks

$\frac{2\sqrt{3}}{\sqrt{5}+2\sqrt{6}} \times \frac{\sqrt{5}-2\sqrt{6}}{\sqrt{5}-2\sqrt{6}}$

Like I said $(a+b)(a-b)=a^2-b^2$. What a and b are should be obvious. Take it from here.