AP Calculus AB: 4.1.1 A Shortcut for Finding Derivatives
This content introduces the power rule, a shortcut for finding derivatives of functions where variables are raised to rational powers. It explains how to apply the rule and includes examples involving both positive and negative exponents, as well as how to find slopes of tangent lines using derivatives.
Shortcut for Finding Derivatives
Using the definition to find the derivative of a function is very time-consuming. However, when dealing with variables raised to rational powers, there is a shortcut you can use that makes finding derivatives easier. This shortcut is called the power rule.
The power rule states that if N is a rational number, then the function f(x) = x^N is differentiable and f’(x) = Nx^N-1
Key Terms
Shortcut for Finding Derivatives
Using the definition to find the derivative of a function is very time-consuming. However, when dealing with variables raised to rational p...
note
This is a table of some functions and their derivatives.
If you look carefully, you can see a pattern between the
powers ...
Suppose f(x)=x^−3. What is f′(x)?
f′(x)=−3x^-4
You can use the power rule to take the derivative of functions with exponents expressed as:
negative integers
natural numbers
negative fractions
Suppose f(x)=x^5/2. What is the slope of the line tangent to f at x=4?
20
The power rule is used to find the derivative of what sorts of functions?
Functions of x raised to a power.
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| Term | Definition |
|---|---|
Shortcut for Finding Derivatives |
|
note |
|
Suppose f(x)=x^−3. What is f′(x)? | f′(x)=−3x^-4 |
You can use the power rule to take the derivative of functions with exponents expressed as: |
|
Suppose f(x)=x^5/2. What is the slope of the line tangent to f at x=4? | 20 |
The power rule is used to find the derivative of what sorts of functions? | Functions of x raised to a power. |
The power rule can be expressed as: | [xn]′=nx^n−1 |
When using the power rule, the original coefficient: | Is multiplied by the original exponent |
Suppose f(x)=x^7/2.Find the equation of the line tangent to f(x)at (2,8√2). | y=(14√2)x−20√2 |
Suppose f (x) = x^ −4/3. What is the slope of the line tangent to f at x = 2? | -^3√4 /6 |
Suppose f (x) = −x ^−1. What is the slope of the line tangent to f at x = 3? | 1/9 |
Suppose f(x)=x7. What is the slope of the line tangent to f at x=2? | 448 |
Find the derivative of f if f (x) = x ^50. | f′(x)=50x^49 |
When using the power rule, the original exponent: | is reduced by one |