For this case we have the following polynomial:

To simplify, we must add terms whose exponent is the same, that is:
Given:

Where:
a, b, c are the coefficients of the terms of the polynomial
x: It is the variable
n, 3: Are the exponents associated with the terms
We can simplify the form:

That said, we can simplify the given polynomial in the following way:

Answer:
