The easiest terms to check are the first (8x)(2x²) = 16x³ and the last (-5)(-6) = 30. This check eliminates the first choice. The remaining choices differ only in the sign and coefficient of the squared term, so that is the one we need to find.
The squared term will be the sum of the products of factors whose degrees total 2:
(8x)(-5x) + (-5)(2x²) = -40x² -10x² = -50x²
The appropriate choice is
16x³ -50x² -23x +30