Chapter 7: Problem 52
For exercises 49-52, simplify. $$ \frac{m^{3}}{m^{2}+12 m+27}+\frac{27}{m^{2}+12 m+27} $$
Short Answer
Expert verified
\[ \frac{m^2 - 3m + 9}{m + 9} \]
Step by step solution
01
Identify Common Denominator
Notice that both fractions have the same denominator: \[ m^2 + 12m + 27 \].
02
Combine the Numerators
Since the denominators are the same, combine the numerators: \[ \frac{m^3 + 27}{m^2 + 12m + 27} \]
03
Factor the Numerator
Factor the numerator, which is a sum of cubes: \[ m^3 + 27 = (m + 3)(m^2 - 3m + 9) \]
04
Factor the Denominator
Factor the denominator: \[ m^2 + 12m + 27 = (m + 3)(m + 9) \]
05
Simplify the Expression
Rewrite the expression with the factors and cancel the common factor \ (m + 3): \[ \frac{(m + 3)(m^2 - 3m + 9)}{(m + 3)(m + 9)} \].Canceling out \ (m + 3), we get: \[ \frac{m^2 - 3m + 9}{m + 9} \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Common Denominator
To simplify algebraic expressions involving fractions, the first step often involves finding a common denominator. A common denominator is a shared denominator between fractions, which allows us to combine the fractions easily.
In our problem, the given fractions both have:
In our problem, the given fractions both have:
- The same denominator: \b \b
- This checks off the first step and ensures the denominators align perfectly.
Sum of Cubes
The sum of cubes is a special type of polynomial factoring that you need to recognize. Generally, an expression like \( a^3 + b^3 \) can be factored into \( (a + b)(a^2 - ab + b^2) \).
In our problem, the numerator \( m^3 + 27 \) is actually the sum of cubes:
In our problem, the numerator \( m^3 + 27 \) is actually the sum of cubes:
- Identify: \( m \to m \) and \( b = 3 \) since \( 27 = 3^3 \)
- Apply the formula: \( (m + 3)(m^2 - 3m + 9) \)
Factoring Polynomials
Factoring polynomials is another key step in simplifying algebraic expressions. This process involves breaking down a polynomial into simpler 'factor' polynomials whose product is the original polynomial.
Looking at the denominator in our problem: \( m^2 + 12m + 27 \), we proceed by:
Looking at the denominator in our problem: \( m^2 + 12m + 27 \), we proceed by:
- Finding numbers that multiply to 27 and add up to 12. These numbers are 3 and 9
- Expressing the polynomial as: \( (m + 3)(m + 9) \)
Canceling Common Factors
Canceling common factors simplifies fractions. When a numerator and denominator share a common polynomial factor, they can be canceled out.
For our fraction, we have \( \frac{(m + 3)(m^2 - 3m + 9)}{(m + 3)(m + 9)} \):
For our fraction, we have \( \frac{(m + 3)(m^2 - 3m + 9)}{(m + 3)(m + 9)} \):
- The common factor is \( (m + 3) \)
- We cancel it out from both the numerator and the denominator.