Chapter 12: Problem 75
In Exercises 71-78, find \(\lim_{h \to 0}\ \dfrac{f(x+h)-f(x)}{h} \). \(f(x) = x^2-3x\)
Short Answer
Expert verified
The solution is \(2x - 3\).
Step by step solution
01
Calculation of f(x + h)
First, substitute \(x + h\) into \(f(x)\) to get \(f(x + h) = (x + h)^2 - 3(x + h)\). Apply the power rule ((a + b)^2 = a^2 + 2ab + b^2) and distribute the term -3 to get \(f(x + h) = x^2 + 2xh + h^2 - 3x - 3h\).
02
Calculation of f(x + h) - f(x)
Next, subtract \(f(x)\) from \(f(x + h)\), which yields \((x^2 + 2xh + h^2 - 3x - 3h) - (x^2 - 3x) = 2xh + h^2 - 3h\).
03
Simplification of the Fraction
Now, divide \(2xh + h^2 - 3h\) by \(h\), and simplify the fraction by cancelling out \(h\), to get \(2x + h - 3\). Next, apply the limit \( h \to 0 \) to this expression to get the answer, \(2x - 3\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Derivative
The derivative represents a fundamental concept in calculus, specifically showcasing how a function changes at any given point. Think of it as the function's slope or gradient at a particular point. When you compute a derivative, you're trying to understand how changes in the input of a function lead to changes in the output. This is vital for grasping more advanced math concepts.
To find a derivative, you often use the difference quotient, expressed as:
To find a derivative, you often use the difference quotient, expressed as:
- \( \lim_{h \to 0}\ \frac{f(x+h) - f(x)}{h} \)
Differential Calculus
Differential calculus revolves around computing the derivative of functions, which allows us to understand and quantify change in mathematical contexts. It plays a crucial role in both theoretical and applied mathematics, forming the backbone of many scientific calculations. At its core, differential calculus is concerned with two main ideas:
- Instantaneous Rate of Change: This is essentially what a derivative is. It provides a snapshot of how rapidly a quantity is changing at any given moment, as opposed to over an interval.
- Function Behavior: Derivatives help describe the shape and behavior of function graphs, such as identifying peaks (maximums), troughs (minimums), and where the graph is increasing or decreasing.
Limit of a Function
In calculus, the limit of a function helps us understand the behavior of the function as it gets closer to a particular point. This is pivotal when analyzing derivatives and helps form the core of many calculus concepts. A limit can be seen as a function's intended destination or goal as it approaches a specific x-value.
Mathematically, we express this as:
Mathematically, we express this as:
- \( \lim_{x \to c} f(x) = L \)
Rate of Change
The rate of change concept is a familiar idea to many, often understood as how one quantity varies in relation to another. It encapsulates the essence of a derivative quite well, shedding light on how responsive a function is to changes in its inputs. The rate of change can be constant or variable, depending on the nature of the function.
For example, a linear function has a constant rate of change, visualized as a straight line with a uniform slope. However, a function like \( f(x) = x^2 - 3x \), unfolding in this exercise, has a variable rate of change. The derivative \( 2x - 3 \) shows how the rate adapts depending on the value of \( x \). This provides critical information about the dynamic behavior of a function, aiding in predictions and rationale for systems in motion or change.
For example, a linear function has a constant rate of change, visualized as a straight line with a uniform slope. However, a function like \( f(x) = x^2 - 3x \), unfolding in this exercise, has a variable rate of change. The derivative \( 2x - 3 \) shows how the rate adapts depending on the value of \( x \). This provides critical information about the dynamic behavior of a function, aiding in predictions and rationale for systems in motion or change.