Chapter 7: Problem 13
Find the LCD for the fractions in each list. $$ \frac{17}{15 y^{2}}, \frac{55}{36 y^{4}} $$
Short Answer
Expert verified
The LCD is \( 180y^4 \).
Step by step solution
01
Identify the denominators
The denominators in the given fractions are \( 15y^2 \) and \( 36y^4 \).
02
Prime factorize the numerical coefficients
Prime factorize the numbers 15 and 36: \( 15 = 3 \times 5 \) and \( 36 = 2^2 \times 3^2 \).
03
Identify the variables
The variable parts of the denominators are \( y^2 \) and \( y^4 \).
04
Combine the highest powers of each prime factor
The highest powers of 2, 3, 5, and \( y \) present in the factorization are \( 2^2 \), \( 3^2 \), 5, and \( y^4 \).
05
Write the Least Common Denominator
Multiply these together to find the LCD: \[ 2^2 \times 3^2 \times 5 \times y^4 = 4 \times 9 \times 5 \times y^4 = 180y^4 \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Prime Factorization
Prime factorization is a method used to express a number as the product of its prime factors. Primes are numbers that only have two positive divisors: 1 and themselves. For example, to factorize 15, you break it down into 3 and 5鈥攂oth prime numbers, so 15 becomes 3 脳 5. Similarly, 36 can be factored as 2 脳 2 脳 3 脳 3 or in exponential form as 2虏 脳 3虏. This step is crucial because it allows us to see the underlying structure of the numbers. For our exercise, the factorization lets us identify all the prime factors involved in the denominators, which is essential for finding the Least Common Denominator (LCD). Understanding the individual components makes it simpler to combine the highest powers of each element in later steps.
Comparing Denominators
Once we have the prime factorizations, the next step is to compare the denominators. In our example, the denominators are 15y虏 and 36y鈦. First, focus on the numerical coefficients: 15 is 3 脳 5, and 36 is 2虏 脳 3虏. Next, incorporate the variable parts: y虏 and y鈦. By isolating and understanding each component鈥攂oth the numerical coefficients and the variable parts鈥攚e can more easily see what needs to be combined to find the LCD. This comparison highlights the importance of being meticulous in identifying each element that constitutes the denominators.
Highest Powers of Prime Factors
In order to find the Least Common Denominator (LCD), we need to combine the highest powers of each prime factor present in the denominators. Let鈥檚 break it down: For the prime number 2, the highest power we need is 2虏 (from 36). For the prime number 3, the highest power is 3虏 (also from 36). For the prime number 5, the highest power is 5 (from 15). For the variable y, the highest power present is y鈦. By collecting these highest powers, we ensure that both denominators can be evenly divided into the LCD. Combining them correctly is the next critical step.
Multiplying Factors
To find the LCD, we multiply the highest powers of all the prime factors and variable parts identified. In our example, we take 2虏, 3虏, 5, and y鈦 and multiply them together:
- 2虏 = 4
- 3虏 = 9
- 5 = 5
- y鈦 = y鈦