Question

Which relation is not a function?

a) y = 1x + 7
by=- 4(x + 3)2 + 10
c) -2y = - 3x + 9
d) x2 + y2 = 25

Answer 1

d) x^2 + y^2 = 25.

Explanation:

D is the equation of a circle so it fails the vertical line test for a function. If a relation is a function then any vertical line passing through it's graph will only intersect it once. This is not true of a circle.

Answer 2

x^2+y^2=25

Explanation:

x^2+y^2=25 graphs a circle. A relation is a function if every x only has one y value. This is not true in a circle.