Terry F. answered 04/04/19
PhD, MBA, MA(math) Math, Statistics, Economics,Finance, Physics, Comp.
What is the definition of a function? For each x there is one and only one 5. So for your equation:
y = 1/2 (x-2) - 6 this is indeed true. Take any x, say x = 4, Then y = 1/2 ( 4-2) - 6 = -5 one value.
This is not true for the equation of a circle centered at the origin with radius =3 given by:
x2 + y2 = 9 When x = 3, y = +3 or -3 Two values of y for one value of x. You can also
use the vertical line test. For a function, a vertical line drawn through a graph of the function will
intersect the graph at only one point.