Is this a mistake on my part or theirs? I'm not sure if I'm the one making the mistake, or my math book. It looks like the negative sign completely disappeared.
$$\frac{3x^2}{-\sqrt{18}} \cdot \frac{\sqrt{2}}{\sqrt{2}} = \frac{3x^2\sqrt{2}}{-\sqrt{36}} = \frac{3x^2\sqrt{2}}{6} = \frac{x^2\sqrt{2}}{2}$$
Here is the original image.
Also, I am new to Stackexchange, so tell me if I am doing something wrong.

It's probably them. It starts out correct, but when they go to take the negative square root of 36, there was an error. The correct approach is (or should I say, should be): $$\frac{3x^2}{-\sqrt{18}}\cdot \frac{\sqrt{2}}{\sqrt{2}} = \frac{3x^2\sqrt{2}}{-\sqrt{36}} = \frac{3x^2\sqrt{2}}{-6} = -\frac{x^2\sqrt{2}}{2}$$ This is because $-\sqrt{36}$ is actually $-(\sqrt{36})$. Or you could just apply the fraction rule and make it negative and go from there. It'll still give you the same answer.
