To determine which functions are exponential functions, we need to look for functions that can be expressed in the form \( y = a^x \), where \( a \) is a positive constant.
Let's analyze each option:
A. \( y = x^3 - 6x \)
This is a polynomial function, not exponential.
B. \( y = 2^x \)
This is an exponential function because it fits the form \( a^x \) with \( a = 2 \).
C. \( y = x^3 \)
This is also a polynomial function, not exponential.
D. \( y = 2x + 2 \)
This is a linear function, not exponential.
E. \( y = \left( \frac{1}{4} \right)^x \)
This is an exponential function because it fits the form \( a^x \) with \( a = \frac{1}{4} \).
F. \( y = \frac{1}{2} x^2 e \)
This is a polynomial function (specifically a quadratic multiplied by a constant), not exponential.
Based on the analysis, the exponential functions from the options provided are:
B. \( y = 2^x \)
E. \( y = \left( \frac{1}{4} \right)^x \)
So the correct selections are B and E.