## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

As we can see as $x$ gets closer and closer to $4$ from the left, the value of the function (the y-value) gets closer and closer to $4$. But, as we can see as $x$ gets closer and closer to $4$ from the right, the value of the function (the y-value) gets closer and closer to $2$. Thus the limits from the two sides differ, thus the limit does not exist.