# Homework Help: Solving Surds

1. Mar 20, 2008

### binomialgurl

im having trouble trying to figure out a problem. can someone help me.

(2/6 -root3)^2 - (2/6+root3)^2

if that makes sense to anyone help.

I think that the denominator of both has to be rationalised but do i expand the squared brackets first or later or what?

any ideas welcome thanks

2. Mar 20, 2008

### tramtran111

I think you can use the difference of 2 squares a^2 - b^2 = ( a+b) (a-b). good luck!

3. Mar 20, 2008

### Tedjn

Do you mean

$$\left(\frac{2}{6-\sqrt{3}}\right)^2 - \left(\frac{2}{6+\sqrt{3}}\right)^2$$

What are you supposed to do with this? Simplify?

4. Mar 21, 2008

### PuzzledMe

Don't expand first. Use a^2 - b^2 = (a+b) (a-b) as tram said, at denominator, remember to do two times due to the square. This is to make denominator a whole number. Account for the multiplication for the numerator too.

5. Mar 23, 2008

### binomialgurl

I am supposed to evaluate it.
And thanks for all the advice by the way.

Last edited: Mar 23, 2008