Answer
81
Work Step by Step
Plugging in the given values of x and simplifying, we find:
$$\frac{1}{3}x^4-2x^3 \\ \frac{1}{3}\cdot \:3^4-2\cdot \:3^3 =-27 \\ \frac{1}{3}\left(-3\right)^4-2\left(-3\right)^3=81$$
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