A function that represents the volume of a cardboard box is V(x) = -0.65x^3 + 4x^2 + 3x, where x is the width of the box. Determine the width that will maximize the volume. What are the restrictions on the width?

The answer is 4.45 and domain is 0<x<6.83

My teacher didnt teach me how to find the vertex and maximum of cubic equations yet so i just factored out the x and used it as a quadratic equation and put it in vertex form. But that didn't work HELP!

Two soccer players start at opposite sides of an 80-m field. One runs at 4 m/s and the other runs at 5 m/s. If they run back and forth for 15 mins, how many times will they pass each other?

**The answer is 25 but I keep getting 45. I didn't use any equations to use this but I keep messing with the numbers and end up at 45.