Question

Which equation represents a function?
y2 + x = 6
y4 + x3 = 3
y – x2 = 4
y2 – x2 = 7
y2 + x2 = 7

Answer 1

$$\Huge y-x^2=4$$ Do you want to know why?

Answer 2

Why ?

Answer 3

What word do you need to define, to answer that question?

Answer 4

Learning Algebra is the first step to critical thinking.

Answer 5

http://www.mathsisfun.com/sets/function.html