So... first off, we sort the dividend, the numerator, in descending order... so, looking at the exponents in this one, is already sorted in descending order, from 4 down to 1, so that's done.
then the divisor, we have x+3, that means x + 3 = 0, x = -3,
so, we'll be using -3 for the synthetic division then.

and now, we'll use those coefficients, dropping the exponents of the polynomial by one, and the remainder, remains as a fraction with the divisior of x+3.