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.

Be cautious about the negative sign,
$$\frac{3x^{2}}{-\sqrt{18}} \times \frac{\sqrt{2}}{\sqrt{2}}=- \frac{3x^{2}}{\sqrt{18}} \times \frac{\sqrt{2}}{\sqrt{2}} =- \frac{3x^{2}}{3\sqrt{2}} = -\frac{x^{2}}{\sqrt{2}}$$
Maybe, there is a typo in the textbook.
