The function y = 4x is an exponential growth function. The graph of the function increases as x increases. The variable x is a (n)

coefficient

term

exponent

factor

The tang be a factor

There are two ways to approach this depending on your level of math, the second way applies only to people who have already begun calculus. The third paragraph gives the answer for a below-calculus student.

First, tell whatever idiot that asked you this that y = 4x is the equation of a line in 2D or a plane in 3D (never exponential growth). As such, there is no mathematically correct answer to this question unless we consider X to be not a variable, but a function.

I don't know what level math you are in so I'll solve this for you both ways. If you are below calculus, the idiot teaching you wants you to say that X is an exponent (if it's exponential growth, there HAS to be an exponent, there isn't one shown, therefore it must be X).

If you are in calculus or above, X denotes an independent function (not a variable). As such, you know that all things in that equation (minus the equals sign) are terms, variables are not coefficients, and X is not denoted to be an exponent. Therefore, the only remaining option is a factor.