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Power Rule for Differentiation

Prerequisites

Definition of a Derivative | \(f'(x) = \lim_{h \to 0} \frac{f(x + h) - f(x)}{h}\)

Description

This equation shows how to find the derivative of a polynomial term. It is often used in conjunction with the Addition Rule for Differentiation to take the derivative of a polynomial.

\[\frac{\htmlClass{sdt-0000000102}{\:d}}{\htmlClass{sdt-0000000102}{\:d} \htmlClass{sdt-0000000003}{x}}(\htmlClass{sdt-0000000121}{a} \htmlClass{sdt-0000000003}{x}^{\htmlClass{sdt-0000000015}{k}}) = \htmlClass{sdt-0000000015}{k} \htmlClass{sdt-0000000121}{a} \htmlClass{sdt-0000000003}{x}^{\htmlClass{sdt-0000000015}{k} - 1}\]

Symbols Used:

This is a symbol for any generic variable. It can hold any value, whether that be an integer or a real number, or a complex number, or a matrix etc.

\( k \)

This symbol represents any given integer, \( k \in \htmlClass{sdt-0000000122}{\mathbb{Z}}\).

\( \:d \)

This is the symbol for a differential. It represents an infinitesimally small (infinitely close to zero) change in whatever variable it is with respect to.

\( a \)

This is a symbol for any generic constant. It can hold any numerical value

Derivation

Consider the definition of a derivative:

\[\htmlClass{sdt-0000000065}{f'(x)} = \htmlClass{sdt-0000000101}{\lim}_{\htmlClass{sdt-0000000067}{h} \to 0} \frac{\htmlClass{sdt-0000000096}{f}(\htmlClass{sdt-0000000003}{x} + \htmlClass{sdt-0000000067}{h}) - \htmlClass{sdt-0000000096}{f}(\htmlClass{sdt-0000000003}{x})}{\htmlClass{sdt-0000000067}{h}}\]

More coming soon...

Example

Consider \(\htmlClass{sdt-0000000096}{f}(\htmlClass{sdt-0000000003}{x}) = \htmlClass{sdt-0000000003}{x}^2\), what is \( \htmlClass{sdt-0000000065}{f'(x)} \)?

Values:

\(\htmlClass{sdt-0000000121}{a} = 1\)

\(\htmlClass{sdt-0000000015}{k} = 2\)

We can now plug these values in to get:

Solution

\[ \htmlClass{sdt-0000000065}{f'(x)} = (2)(1)\htmlClass{sdt-0000000003}{x}^{2 - 1} = 2\htmlClass{sdt-0000000003}{x} \]