So my understanding from this you have to make it y = mx + b so m stands for the slope there’s different ways to find it as shown in the first picture. I’ll try to make another comment since this only lets me take one picture at a time.
Simplify the given expression as shown below

<h2>Therefore, the answer is 12x^5-15x^2</h2>
........hmmmmmmmmmmmm.......