Answer:
#5
It is not a function because the some x-values can have more than one possible y-value. The x-values can have the positive and negative y-value.
Explanation:
The equation is the equation for a circle. When you graph a circle, it does not pass the vertical line test.
Example: if x is 6
6² + y² = 100
36 + y² = 100
y² = 100 - 36
y² = 64
y = ± √64 This is true because: (-8)² = 64 AND 8² = 64
y = -8 OR 8
By the way, for #4 it is not a function.
The points (13, 4) and (13, -4) mean that x will have more than one y value. The x-value 13 will have y-values 4 and -4.