Slope is the steepness of a line. A positive slope rises; a negative slope falls. Another term for slope is gradient.
For a straight line, the slope (m) is constant and represented by the difference in the vertical direction (y) divided by the difference in the horizontal direction (x):
The delta, Δ, represents the difference in values between any two points in the x or y direction for straight line. For a curve, the delta, Δ, represents the difference in values for two points in very close proximity to each other.
For a straight line, another way of representing the slope (m) is as follows:
where the two points are located at (x1, y1) and (x2, y2).
Introduction to derivative
If a function has value f(x) at x and f(x + h) at x + h with h > 0 than the slope of the line joining (x,f(x)) to (x + h,f(x + h)) is,
The slope of the line that meets (is tangential to) f(x) at x is the limit as h tends to zero, or,
which is denoted f'(x), which is called the derivative of f(x).