What’s a Derivative?

A more helpful question may be

“What question does a derivative answer?”

Suppose the a variable y depends on x (so that y is a function of x).

**Question:** If x changes from 102 to 103.4, how much does y change?

**Answer: **You need the derivative.

Change in y (Derivative) (Change in x)

We have

(Change in x) = = 103.4-102 = 1.4.

Therefore

(Change in y) = Derivative 1.4.