Chapter 1: Problem 11
For \(g(u)=3 /(u-2)\), find and simplify \([g(x+h)-\) \(g(x)] / h\).
Short Answer
Expert verified
The simplified expression is \( \frac{-3}{(x-2)(x+h-2)} \).
Step by step solution
01
Plug in the Values
Start by writing out the expression \( [g(x+h) - g(x)] / h \) using the function \( g(u) = \frac{3}{u-2} \). Replace \( u \) with \( x+h \) and \( x \) in \( g(u) \).Thus, \[g(x+h) = \frac{3}{(x+h)-2} = \frac{3}{x+h-2}\]\[g(x) = \frac{3}{x-2}\]So, the expression becomes \[\frac{3}{x+h-2} - \frac{3}{x-2}\] divided by \( h \).
02
Simplify the Expression
To simplify \( \frac{3}{x+h-2} - \frac{3}{x-2} \), find a common denominator. The common denominator here is \[(x+h-2)(x-2).\]Rewrite each fraction:\[\frac{3}{x+h-2} = \frac{3(x-2)}{(x+h-2)(x-2)}\]\[\frac{3}{x-2} = \frac{3(x+h-2)}{(x-2)(x+h-2)}\]Now subtract these fractions:\[\frac{3(x-2) - 3(x+h-2)}{(x-2)(x+h-2)}\]
03
Simplify the Numerator
Simplify the expression in the numerator:\[3(x-2) - 3(x+h-2) = 3x - 6 - (3x + 3h - 6)\]Distribute and combine terms:\[= 3x - 6 - 3x - 3h + 6 = -3h\]
04
Divide by h
Now substitute back into the main expression:\[\frac{-3h}{(x-2)(x+h-2)} \times \frac{1}{h}\]This simplifies to \[\frac{-3}{(x-2)(x+h-2)}\] after canceling \( h \) in the numerator and denominator.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Difference Quotient
The difference quotient is a critical concept in calculus, as it forms the basis for understanding derivatives, which describe how a function changes at any given point. In our exercise, we're dealing with the difference quotient expressed as \( \frac{g(x+h) - g(x)}{h} \). Let's break this down:
- First, substitute specific values into the function \( g(u) \). For our problem, this means replacing \( u \) with both \( x+h \) and \( x \) to get their respective functions.
- Then, calculate \( g(x+h) \) and \( g(x) \), leading to an expression \( \frac{3}{x+h-2} - \frac{3}{x-2} \).
- Finally, divide the difference by \( h \) to establish the difference quotient itself.
Function Simplification
Simplifying functions is a critical skill in calculus that involves making an expression easier to work with. This typically means reducing a complex fraction or expression to a more manageable form. Here's how we simplify the expression from the exercise:
- Identify the need for a common denominator to add or subtract fractions. For example, for the fractions \( \frac{3}{x+h-2} \) and \( \frac{3}{x-2} \), the common denominator becomes \((x+h-2)(x-2)\).
- Re-express each fraction with this common denominator, turning the expression into \( \frac{3(x-2) - 3(x+h-2)}{(x+h-2)(x-2)} \).
- Focus on simplifying the numerator by distributing and combining like terms, resulting in \(-3h\).
Rational Functions
Rational functions are functions expressed as the quotient of two polynomials. The function \( g(u) = \frac{3}{u-2} \) from our exercise is a simple example. Here we explore some key points about rational functions:
- The denominator cannot be zero, so in \( g(u) \), \( u-2 \) cannot equal zero. This implies \( u \) cannot be 2, helping identify potential points of discontinuity.
- These functions often require simplification techniques, involving operations like addition and subtraction of fractions, always demanding a common denominator.
- Simplification processes lead to clearer interpretations of the function's behavior, especially when calculating values around problematic points (like vertical asymptotes).