Answer
(a) y = 3x is the green one.
(b) y = $3^{x}$ is the blue one.
(c) y = $x^{3}$ is the pink one.
(d) y = $\sqrt[3] x$ is the black one.
Work Step by Step
y = 3x is a linear function. It must be a straight line.
y = $3^{x}$ is an exponential function where the base 3 $\gt$ 1.
y = $x^{3}$ is a power function. It's also odd, so it's positive if x $\gt$ 0 and negative if x $\lt$ 0.
y = $\sqrt[3] x$ is a root function.
