A reflection of a function is a transformation that flips a graph over some line. This line is called the line of reflection and is commonly either the $x\text{-}$ or $y\text{-}$axis. A reflection in the $x\text{-}$axis is achieved by changing the sign of the $y\text{-}$coordinate of every point on the graph. The $y\text{-}$coordinate of all $x\text{-}$intercepts is $0.$ Thus, changing the sign of the function value at $x\text{-}$intercepts makes no difference — any $x\text{-}$intercepts are preserved when a graph is reflected in the $x\text{-}$axis. A reflection in the $y\text{-}$axis is instead achieved by changing the sign of every input value. When $x=0,$ which is at the $y\text{-}$intercept, this reflection does not affect the input value. Therefore, the $y\text{-}$intercept is preserved by reflections in the $y\text{-}$axis. The following table illustrates the different types of reflections that can be done to a function.

Transformations of $f(x)$
Reflections	In the $x\text{-}$axis $y=\text{-}f(x)$
	In the $y\text{-}$axis $y=f(\text{-}x)$