Answer:
(-∞, 12].
Explanation:
To graphically determine the range of a function, we'll just have to determine from what y value to what other y value the function moves, vertically.
So as you can tell from the image, the function's highest point is y=12, so this means that we have one side of our interval. Then, we can see than the function goes all the way down to negative infinity, hence, we may conclude that the other side of our interval is negative infinity.
Hence, the range of this function can be represented using the following interval:
(-∞, 12].
Take a look to the square bracket that we place next to the "12" and the parenthesis next to -∞. The square bracket next to the "12" means that the function contains the value of 12, 12 can be a result of evaluating this function with an unknown "x" value. On the other hand, we use parenthesis for infinity since it's a standard procedure in mathematics, it means that the function reaches negative infinity. We always use parenthesis next to infinity symbols, no matter their sign.
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The mathematical tool we used to represent the function's range in this answer is called "interval notation". Feel free to research a little bit more about this topic, since it's one of the most common ways to represent a function's domain and range in math.