How to solve this algebraically showing work

Question

5y^2-x=15

Solving this algebraically showing work wether it is a function

Answer 1

5y^2 -x = 15

5y^2 = x+15

y^2 = x/5 + 3

y = + or - sqr(x/5 +3)

there are 2 y values for any x value (except for x=-15)

it fails the vertical line test. It's a rightward opening parabola. If a vertical line can cut the graph in more than one intersection point, it's not a function.