1. We are asked to simplify the expression $$\left( \frac{-a}{b} \right)^2$$. 2. The formula for squaring a fraction is $$\left( \frac{x}{y} \right)^2 = \frac{x^2}{y^2}$$. 3. Applying this to our expression, we get: $$\left( \frac{-a}{b} \right)^2 = \frac{(-a)^2}{b^2}$$. 4. Squaring the numerator, $$(-a)^2 = (-1)^2 \cdot a^2 = 1 \cdot a^2 = a^2$$. 5. So the expression simplifies to: $$\frac{a^2}{b^2}$$. 6. Therefore, $$\left( \frac{-a}{b} \right)^2 = \frac{a^2}{b^2}$$. This means the negative sign disappears when squaring because $$(-1)^2 = 1$$.