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Ch. 3 - Derivatives
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 3, Problem 3.3.64

Power Rule for negative integers Use the Derivative Quotient Rule to prove the Power Rule for negative integers, that is,
d/dx (x⁻ᵐ) = −mx⁻ᵐ⁻¹
where m is a positive integer.

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Start by expressing the function x^(-m) as a fraction: x^(-m) = 1/x^m.
Apply the Quotient Rule for derivatives, which states that if you have a function in the form of u/v, the derivative is (v * du/dx - u * dv/dx) / v^2.
Set u = 1 and v = x^m. Then, compute the derivatives: du/dx = 0 and dv/dx = m * x^(m-1).
Substitute these into the Quotient Rule formula: (x^m * 0 - 1 * m * x^(m-1)) / (x^m)^2.
Simplify the expression: -m * x^(m-1) / x^(2m) = -m * x^(-m-1), which proves the Power Rule for negative integers.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Derivative Quotient Rule

The Quotient Rule is a method for finding the derivative of a function that is the ratio of two differentiable functions. If you have a function f(x) = g(x)/h(x), the derivative f'(x) is given by (g'(x)h(x) - g(x)h'(x)) / (h(x))^2. This rule is essential for differentiating functions expressed as fractions, such as x⁻ᵐ, which can be rewritten as 1/xᵐ.
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The Quotient Rule

Power Rule for Derivatives

The Power Rule is a basic rule in calculus for finding the derivative of a function of the form f(x) = xⁿ, where n is any real number. The derivative is given by f'(x) = nxⁿ⁻¹. This rule simplifies the process of differentiation and is fundamental for understanding how to handle powers of x, including negative powers.
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Negative Integer Exponents

Negative integer exponents indicate the reciprocal of the base raised to the corresponding positive exponent. For example, x⁻ᵐ is equivalent to 1/xᵐ. Understanding this concept is crucial when applying the Power Rule to negative exponents, as it involves rewriting the expression in a form suitable for differentiation using the Quotient Rule.
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