Question 2328
a function and an equation are hte same thing basically, just that the wording "function" sounds more professional. No doubt a hardened mathematician may say they are NOT the same, but for all intents and purposes they are:

y={{{x^3 + 4x}}} is an equation
f(x)={{{x^3 + 4x}}} is a function

but they are the same!

Plotting...just the same, just instead of "y", you put "f(x)" on the vertical axis.

Grandient of a line is always the same at every point. The gradient of a curve is different as you move along the curve. Both are defined as (change in y)/(change in x).

Jon