Answer
$$-6x^3+4x^2-24x+8.$$
Work Step by Step
We subtract the $x^3$-terms as follows
$$
8x^3-14x^3=-6x^3
$$
then subtract the $x^2$-terms as follows
$$
6x^2-2x^2=4x^2
$$
then subtract the $x$-terms as follows
$$
-15x-9x=-24x
$$
then subtract the constant terms as follows
$$
7+1=8
$$
Hence, the result is
$$-6x^3+4x^2-24x+8.$$
