Chapter 11: Problem 55
Express each of the given expressions in simplest form with only positive exponents. $$(D-1)^{-1}+(D+1)^{-1}$$
Short Answer
Expert verified
The expression simplifies to \(\frac{2D}{(D-1)(D+1)}\).
Step by step solution
01
Rewrite with positive exponents
The expression \[(D-1)^{-1} + (D+1)^{-1}\] can be rewritten with positive exponents as \[\frac{1}{D-1} + \frac{1}{D+1}\] because \(x^{-1}\) is equivalent to \(\frac{1}{x}\).
02
Find a common denominator
To add the fractions \(\frac{1}{D-1}\) and \(\frac{1}{D+1}\), we need a common denominator. The common denominator for these fractions is \[(D-1)(D+1),\] which is the product of the two different denominators.
03
Adjust each fraction to have the common denominator
Rewrite each fraction as \[\frac{1}{D-1} = \frac{D+1}{(D-1)(D+1)}\] and \[\frac{1}{D+1} = \frac{D-1}{(D-1)(D+1)}.\] Now both fractions have the same denominator.
04
Add the fractions
Add the fractions \[\frac{D+1}{(D-1)(D+1)} + \frac{D-1}{(D-1)(D+1)}.\] The sum of the numerators is \[(D+1) + (D-1) = 2D.\] Therefore, \[\frac{D+1}{(D-1)(D+1)} + \frac{D-1}{(D-1)(D+1)} = \frac{2D}{(D-1)(D+1)}.\]
05
Simplify the expression
The simplified expression is \[\frac{2D}{(D-1)(D+1)}.\] There are no common factors in the numerator and denominator to cancel, so this is the simplest form.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Exponents
Exponents are essential components in mathematics that express repeated multiplication of a base number. When dealing with exponents, it's critical to understand how they affect expressions and operations.
- "Positive exponents" indicate how many times to multiply the base by itself.
- "Negative exponents" suggest taking the reciprocal of the base raised to the corresponding positive exponent.
Common Denominator
Finding a common denominator is crucial when adding or subtracting fractions to ensure they have a uniform base for the operation. Here's how you can find a common denominator:
- Identify the denominators of your fractions.
- Calculate the least common multiple (LCM) of these denominators.
- In expressions like \(\frac{1}{D-1} + \frac{1}{D+1}\), multiply the different denominators together to find a common base: \((D-1)(D+1)\).
Fraction Addition
Once fractions share a common denominator, the addition process becomes straightforward:
- Align each fraction so they have the same denominator.
- Add the numerators together while maintaining the common denominator.
Rational Expressions
Rational expressions extend the concept of fractions to polynomials in the numerator and denominator. These expressions require careful handling:
- Simplification often involves reducing the expression to its simplest terms.
- Factor both the numerator and the denominator to spot any common factors that could be canceled.