Answer:
yes.
Explanation:
The definition of a function: "A function is defined as a relation between a set of inputs having one output each."
This means each x can only have 1 y value. You can check if this is a function using the vertical line test. To do the vertical line test draw vertical lines through the graph of the expression. If you even hit 2 points with a vertical line it is NOT as function.
The graph is of an upward facing parabola so it will be a function. We can graph and check this with the VLT which it passes.