# Thread: Expressing surds into a form

1. ## Expressing surds into a form

Express $(\frac{1}{\sqrt{10}} - \frac{\sqrt{40}}{3}) \times \frac{45}{\sqrt{5}}$ in the form $a\sqrt{2}$, where $a$ is a constant.
I can't seem to get the correct answer that is $-\frac{51}{2}\sqrt{2}$
My working:

(excuse the lack of latex please )

Any help would be greatly appreciated, thanks in advance!

2. Originally Posted by caramelcake
I can't seem to get the correct answer that is $-\frac{51}{2}\sqrt{2}$
My working:

(excuse the lack of latex please )

Any help would be greatly appreciated, thanks in advance!
in the line with the second equal sign, 20/30 should be $\frac {20 \sqrt{10}}{30}$

3. ## Thanks

Thank you! I can get the answer now.