Chapter 12: Problem 105
For the following exercises, find the average rate of change \(\frac{f(x+h)-f(x)}{h}\) $$ f(x)=\sqrt{x} $$
Short Answer
Expert verified
The average rate of change is \( \frac{1}{\sqrt{x+h} + \sqrt{x}} \).
Step by step solution
01
Substitute Function into Formula
The average rate of change formula given is \( \frac{f(x+h)-f(x)}{h} \). For the function \( f(x) = \sqrt{x} \), substitute \( x \) and \( x+h \) into the function. Thus, \( f(x+h) = \sqrt{x+h} \) and \( f(x) = \sqrt{x} \).
02
Substitute Values into the Formula
Replace \( f(x+h) \) and \( f(x) \) in the average rate of change formula: \( \frac{\sqrt{x+h} - \sqrt{x}}{h} \). This is our expression to simplify.
03
Rationalize the Numerator
To simplify \( \frac{\sqrt{x+h} - \sqrt{x}}{h} \), multiply the numerator and the denominator by the conjugate of the numerator, which is \( \sqrt{x+h} + \sqrt{x} \), to rationalize it: \( \frac{(\sqrt{x+h} - \sqrt{x})(\sqrt{x+h} + \sqrt{x})}{h(\sqrt{x+h} + \sqrt{x})} \).
04
Simplify the Expression
The numerator will be \((\sqrt{x+h})^2 - (\sqrt{x})^2 = x+h-x = h\). So, after rationalizing, we have \( \frac{h}{h(\sqrt{x+h} + \sqrt{x})} \).
05
Cancel Common Terms
Observe that \( h \) in the numerator and denominator cancels out: \( \frac{h}{h(\sqrt{x+h} + \sqrt{x})} = \frac{1}{\sqrt{x+h} + \sqrt{x}} \). This is the simplified average rate of change.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Rationalizing the Numerator
When working with expressions such as \( \frac{\sqrt{x+h} - \sqrt{x}}{h} \), rationalizing the numerator is a crucial step. This essentially means making the numerator a rational expression.To do this, we multiply both the numerator and the denominator by the conjugate of the numerator. The conjugate of the numerator \( \sqrt{x+h} - \sqrt{x} \) is \( \sqrt{x+h} + \sqrt{x} \). The purpose of this multiplication is to eliminate the radicals from the numerator.### How It Works:
- Multiply the numerator by its conjugate: \((\sqrt{x+h} - \sqrt{x})(\sqrt{x+h} + \sqrt{x})\).
- Use the difference of squares formula to simplify: \(a^2 - b^2 = (a-b)(a+b)\), where \(a = \sqrt{x+h}\) and \(b = \sqrt{x}\).
- After applying the formula, the numerator becomes \((\sqrt{x+h})^2 - (\sqrt{x})^2 = x+h - x = h\).
Radical Functions
Radical functions include an expression with a variable inside a root, commonly a square root. The function \( f(x) = \sqrt{x} \) is a classic example of a radical function.Understanding radical functions helps in interpreting the behavior of their graphs, which are often curves that start at a point and gradually increase or decrease.### Key Properties of Radical Functions:
- The domain generally includes only non-negative numbers since arithmetic with real numbers does not permit the square root of negatives.
- The range consists of non-negative numbers as well, a reflection of the square root output always being non-negative.
Simplifying Expressions
Simplifying expressions is about reducing them to their simplest forms without changing their values. This often involves combining like terms, reducing fractions, and simplifying roots. In the step-by-step solution provided, simplifying took place after rationalizing the numerator.### Simplification Steps:
- After rationalizing \( \frac{\sqrt{x+h} - \sqrt{x}}{h} \) to \( \frac{h}{h(\sqrt{x+h} + \sqrt{x})} \), we then simplify further by cancelling the common factor \( h \) from the numerator and denominator.
- Thus, the expression simplifies to \( \frac{1}{\sqrt{x+h} + \sqrt{x}} \).
- This reflects a transformation from a more complex to a simpler expression, facilitating easier application in calculus problems.