Chapter 2: Problem 43
Find \(f^{\prime}(x)\) by using the definition of the derivative. $$f(x)=x^{3}+x^{2}$$
Short Answer
Expert verified
The derivative \(f^{\prime}(x)\) is \(3x^2 + 2x\).
Step by step solution
01
Write the definition of the derivative
The derivative of a function \(f(x)\) at any point \(x\) is given by the limit \[ f^{\prime}(x) = \lim_{h \to 0} \frac{f(x + h) - f(x)}{h}. \] To find \(f^{\prime}(x)\) for \(f(x) = x^3 + x^2\), we need to substitute into this formula.
02
Substitute \(f(x + h)\) and \(f(x)\) into the formula
Calculate \(f(x + h)\): \[ f(x + h) = (x + h)^3 + (x + h)^2. \] Expand the expression: \[(x+h)^3 = x^3 + 3x^2h + 3xh^2 + h^3,\] \[(x+h)^2 = x^2 + 2xh + h^2.\] So, \[ f(x + h) = x^3 + 3x^2h + 3xh^2 + h^3 + x^2 + 2xh + h^2. \] Now substitute this back into the derivative definition: \[ \lim_{h \to 0} \frac{(x^3 + 3x^2h + 3xh^2 + h^3 + x^2 + 2xh + h^2) - (x^3 + x^2)}{h}. \] Simplify the expression to get: \[ \lim_{h \to 0} \frac{3x^2h + 3xh^2 + h^3 + 2xh + h^2}{h}. \]
03
Simplify and calculate the limit
Factor \(h\) out of each term in the numerator: \[ h(3x^2 + 3xh + h^2 + 2x + h). \] Cancel the \(h\) in the numerator and denominator: \[ \lim_{h \to 0} (3x^2 + 3xh + h^2 + 2x + h). \] Now calculate the limit by letting \(h \to 0\): \[ 3x^2 + 2x. \]
04
Conclude with the derivative
From the above calculations, the derivative \(f^{\prime}(x)\) of \(f(x) = x^3 + x^2\) is \(3x^2 + 2x\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Polynomial Functions
Polynomial functions are a crucial cornerstone in both algebra and calculus. They consist of variables and coefficients, combined using only addition, subtraction, and multiplication. Each term in a polynomial is a product of a constant coefficient and a variable raised to a non-negative integer power.
- For instance, in the function \(f(x) = x^3 + x^2\), you have two terms: \(x^3\) and \(x^2\).
- The degree of a polynomial is determined by the highest power of the variable, which in this case is 3, making it a cubic polynomial.
- Polynomials can be added, subtracted, and multiplied, and these operations maintain the structure of a polynomial.
The Limit Process and Derivatives
The limit process is a fundamental idea in calculus that is used to define several key concepts, including the derivative. To find the derivative of a function at any point, you need to understand how the function behaves as one variable approaches another.
- The derivative \(f'(x)\) is defined as \(f'(x) = \lim_{h \to 0} \frac{f(x + h) - f(x)}{h}\).
- Essentially, this expression finds the average rate of change of the function \(f(x)\) over a tiny interval \(h\), and then it examines the behavior of \(h\) as it approaches zero.
- Calculating this limit gives us the instantaneous rate of change of the function at point \(x\), which is the essence of the derivative.
Exploring Calculus
Calculus is a field of mathematics that studies continuous change and is divided mainly into two branches: differential calculus and integral calculus. Both parts are interconnected through the fundamental theories of calculus.
- Differential calculus is concerned with the concept of the derivative, which measures how a function changes as its input changes. Calculus lets us compute the derivative in a systematic way using rules and definitions, such as the polynomial derivative rules and the chain rule.
- Integral calculus deals with integration, which is essentially the reverse operation of differentiation. Integration allows us to find areas under curves, among other things.