a ball is thrown into the air. the formula represents the path the ball follows y=0.78x²-4x-8. what is the rate of change from x=2 and x=5?

Question

Plesse help 

Answer 1

You've been given a formula for y.  When x=2, y will be a certain value (you compute it).  We call this y(2). i.e. "y of 2".

 

When x=5, y will have some other value (compute it, too). It's y(5).

 

The rate of change is the difference y(5)-y(2),

divided by the difference in x values, which is of course 3.