Mathematics
Grade 12
15 min
Power rule I
Power rule I
Tutorial Preview
1
Introduction & Learning Objectives
Learning Objectives
State the power rule for derivatives from memory.
Apply the power rule to find the derivative of functions in the form f(x) = cx^n.
Rewrite functions involving radicals and fractions into a power form suitable for differentiation.
Differentiate polynomial functions by applying the power rule and sum/difference rule to each term.
Correctly find the derivative of a constant function.
Calculate the slope of a tangent line to a curve at a specific point using the derivative.
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This tutorial introduces the Power Rule, a fundamental shortcut for finding derivatives without using the lengthy limit definition. Mastering this rule...
2
Key Concepts & Vocabulary
TermDefinitionExample
DerivativeThe derivative of a function, denoted f'(x) or dy/dx, represents the instantaneous rate of change of the function at a specific point. Geometrically, it is the slope of the line tangent to the function's graph at that point.If f(x) represents the position of a car, then its derivative f'(x) represents the car's instantaneous velocity.
Power FunctionA function of the form f(x) = x^n, where n is any real number (positive, negative, or a fraction).f(x) = x^3, g(x) = x^{-2}, h(x) = x^{1/2} (which is \sqrt{x}) are all power functions.
CoefficientA numerical or constant quantity placed before and multiplying the variable in an algebraic expression.In the term 7x^4, the coefficient is 7.
Tangent LineA straight line that 'just touches'...
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Core Formulas
The Power Rule
\frac{d}{dx}(x^n) = n \cdot x^{n-1}
To find the derivative of x raised to a power, bring the exponent down as a multiplier and then subtract one from the original exponent.
The Constant Multiple Rule
\frac{d}{dx}(c \cdot f(x)) = c \cdot \frac{d}{dx}(f(x))
The derivative of a constant multiplied by a function is the constant multiplied by the derivative of the function. The constant 'tags along'.
The Sum/Difference Rule
\frac{d}{dx}(f(x) \pm g(x)) = \frac{d}{dx}(f(x)) \pm \frac{d}{dx}(g(x))
The derivative of a sum or difference of functions is the sum or difference of their individual derivatives. This allows you to differentiate polynomials term by term.
The Constant Rule
\frac{d}{dx}(c) = 0
The derivative of any constant number is ze...
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Challenging
For what value of x is the slope of the tangent line to the curve f(x) = x² - 8x + 3 equal to 2?
A.2
B.8
C.4
D.5
Challenging
Find the equation of the tangent line to the curve y = x³ - 2x at the point (2, 4).
A.y = 10x - 24
B.y = 10x - 16
C.y = 4x - 4
D.y = (3x² - 2)x
Challenging
Find the coordinates of the point(s) on the graph of f(x) = (1/3)x³ - 4x where the tangent line is horizontal.
A.(2, -16/3) only
B.(0, 0) and (2, -16/3)
C.(2, -16/3) and (-2, 16/3)
D.(4, 16/3) and (-4, -16/3)
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