Question

Which of these equations represent functions? Check all that apply.







A.

x2 + y2 = 1








B.

y = 10x3








C.

y = x2 - 3








D.

y = 3x

Answer 1

first one is a circle, doesn't pass the vertical line test, not a function

Answer 2

the rest would be but in truth none of them are functions, they are all equations
what your teacher/book really means is either \(f(x)=3x\) or
\[\{(x,y):y=3x\}\] for example

Answer 3

thus beginning the constant confusion by unsuspecting math students taught by not too competent teacher, of the distinction between equations and functions
not your fault, that is bad education