Identify the function that is exponential. y = −3x5 y = 3x8 y = −3(0.5)x y = −2x4

Please, for clarity, indicate exponentiation using the " ^ " symbol.

y = - 3x^5 ("Negative three times the 5th power of x")

y = 3x^8

y - -3(0.5)^x

y = -2^4

An exponential function has an exponent which is variable, where the base stays constant; the base cannot be a negative number or a zero. The third answer choice is the correct one, as we raise the constant 0.5 to the power x:

y = -3(0.5)^x