Answer:
yes, it is a function.
Explanation:
to be a function every valid value of x must have exactly 1 associated value of y.
to check we do the vertical line test.
imagine a vertical line in the graph (or use a ruler you put on the graph in a vertical way) and move it left and right and see, if the line or the ruler are intersecting the function graph in more than one point.
in our case, wherever we intersect the functional graph with a vertical line, we get only one intersection point.
therefore it is a function.