Answer
$(3,\infty)$
Work Step by Step
The function increases in an interval when, moving from left to right, the y-values continue to get larger for x-values in that interval. For the graph in the question, the y-values increase for all values of $x\gt3$. Since $3$ is not included in the interval as it is represented by an open circle, a parenthesis will be used on its side. On the other end, the symbol $\infty$ will be used which is also always supported by a parenthesis.
Therefore, the function is increasing in the interval $(3,\infty)$.
