Find the LCD -7/a-9/(5a^2)

$\frac{- 7}{a} \cdot \frac{- 9}{5 a^{2}}$

Step 1

Move the negative in front of the fraction.

$- \frac{7}{a} \cdot \frac{- 9}{5 a^{2}}$

Step 2

Move the negative in front of the fraction.

$- \frac{7}{a} \cdot (- \frac{9}{5 a^{2}})$

Step 3

Finding the LCD of a list of values is the same as finding the LCM of the denominators of those values.

$a, 5 a^{2}$

Step 4

Since $a, 5 a^{2}$ contains both numbers and variables, there are two steps to find the LCM. Find LCM for the numeric part $1, 5$ then find LCM for the variable part $a^{1}, a^{2}$ .

Step 5

The LCM is the smallest positive number that all of the numbers divide into evenly.

1. List the prime factors of each number.

2. Multiply each factor the greatest number of times it occurs in either number.

Step 6

The number $1$ is not a prime number because it only has one positive factor, which is itself.

Not prime

Step 7

Since $5$ has no factors besides $1$ and $5$ .

$5$ is a prime number

Step 8

The LCM of $1, 5$ is the result of multiplying all prime factors the greatest number of times they occur in either number.

$5$

Step 9

The factor for $a^{1}$ is $a$ itself.

$a^{1} = a$

$a$ occurs $1$ time.

Step 10

The factors for $a^{2}$ are $a \cdot a$ , which is $a$ multiplied by each other $2$ times.

$a^{2} = a \cdot a$

$a$ occurs $2$ times.

Step 11

The LCM of $a^{1}, a^{2}$ is the result of multiplying all prime factors the greatest number of times they occur in either term.

$a \cdot a$

Step 12

Multiply $a$ by $a$ .

$a^{2}$

Step 13

The LCM for $a, 5 a^{2}$ is the numeric part $5$ multiplied by the variable part.

$5 a^{2}$

Find the LCD -7/a-9/(5a^2)

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