# What is the range of a function?

For example, let's look at the function $y = 2 x$
Since we can plug in any x value and multiple it by 2, and since any number can be divided by 2, the output of the function, the $y$ values, can be any real number.
Let's look at something slightly more complicated, a quadratic in vertex form: $y = {\left(x - 3\right)}^{2} + 4$. This parabola has a vertex at $\left(3 , 4\right)$ and opens upwards, therefore the vertex is the minimum value of the function. The function never goes below 4, therefore the range is $y \ge 4$.