To evaluate the expression we proceed as follows;
(7x³-16x+8)-(4x³-6x²+8x-9)
opening the parenthesis we have:
7x³+0x²-16x+8-4x³+6x²-8x+9
putting like terms together we get:
(7x³-4x³)+(-16x-8x)+(8+9)+(0x²+6x²)
=3x³+6x²-24x+17
the answer is
=3x³+6x²-24x+17