Question

describe when it is and when it is not necessary to use a common denominator when adding, subtracting, multiplying, and dividing rational expressions.

Answer 1

Explanation:

For Adding and Subtraction:

1. Find the denominator (bottom number) of each fraction to find the LCD (least common denominator).

1. Find the denominator (bottom number) of each fraction to find the LCD (least common denominator). 2. find the LCD.

1. Find the denominator (bottom number) of each fraction to find the LCD (least common denominator). 2. find the LCD.3. Find the new numerator (top number) for each fraction. To find the new numerators for each fraction, compare the denominator of each of the original fractions to the LCD and write down everything different about the LCD in the numerator of the fraction. (you should also consider using the letters "LCD" in the denominator instead of the actual LCD as it will be less tempting to reduce them).

1. Find the denominator (bottom number) of each fraction to find the LCD (least common denominator). 2. find the LCD.3. Find the new numerator (top number) for each fraction. To find the new numerators for each fraction, compare the denominator of each of the original fractions to the LCD and write down everything different about the LCD in the numerator of the fraction. (you should also consider using the letters "LCD" in the denominator instead of the actual LCD as it will be less tempting to reduce them). 4. combine the fraction by adding or subtracting the numerators and keeping the LCD. When subtracting, notice that the subtraction sign is moved into the numerator so it can be distributed later if needed.

1. Find the denominator (bottom number) of each fraction to find the LCD (least common denominator). 2. find the LCD.3. Find the new numerator (top number) for each fraction. To find the new numerators for each fraction, compare the denominator of each of the original fractions to the LCD and write down everything different about the LCD in the numerator of the fraction. (you should also consider using the letters "LCD" in the denominator instead of the actual LCD as it will be less tempting to reduce them). 4. combine the fraction by adding or subtracting the numerators and keeping the LCD. When subtracting, notice that the subtraction sign is moved into the numerator so it can be distributed later if needed. 5. simplify the numerator by distributing and combining like terms.

1. Find the denominator (bottom number) of each fraction to find the LCD (least common denominator). 2. find the LCD.3. Find the new numerator (top number) for each fraction. To find the new numerators for each fraction, compare the denominator of each of the original fractions to the LCD and write down everything different about the LCD in the numerator of the fraction. (you should also consider using the letters "LCD" in the denominator instead of the actual LCD as it will be less tempting to reduce them). 4. combine the fraction by adding or subtracting the numerators and keeping the LCD. When subtracting, notice that the subtraction sign is moved into the numerator so it can be distributed later if needed. 5. simplify the numerator by distributing and combining like terms. 6. Factor the numerator if can and replace the letters "LCD" with the actual LCD.

1. Find the denominator (bottom number) of each fraction to find the LCD (least common denominator). 2. find the LCD.3. Find the new numerator (top number) for each fraction. To find the new numerators for each fraction, compare the denominator of each of the original fractions to the LCD and write down everything different about the LCD in the numerator of the fraction. (you should also consider using the letters "LCD" in the denominator instead of the actual LCD as it will be less tempting to reduce them). 4. combine the fraction by adding or subtracting the numerators and keeping the LCD. When subtracting, notice that the subtraction sign is moved into the numerator so it can be distributed later if needed. 5. simplify the numerator by distributing and combining like terms. 6. Factor the numerator if can and replace the letters "LCD" with the actual LCD. 7. simplify or reduce the rational expression of you can. Remember, to reduce rational expressions, the factors must be exactly the same in both the numerator and the denominator.

To Multiply:

• first determine the GCF of the numerator and denominator.
• Then, regrouping the fractions to make fractions equal to One.
• Then, multiply any remaining factors.

To Divide:

• First, rewriting the division as multiplication by the reciprocal of the denominator.
• The remaining steps are the same for multiplication.

Answer 2

9514 1404 393

Answer:

• necessary: addition and subtraction
• not necessary: multiplication and division

Explanation:

For multiplication and division, the denominator of the result is developed as part of the algorithm for performing these operations on rational expressions. For example, ...

(a/b)(c/d) = (ac)/(bd)

(a/b)/(c/d) = (ad)/(bc)

It is not necessary to make the operands of these operations have a common denominator before the operations are performed. That being said, in some cases, the division operation can be simplified if the operands do have a common denominator or a common numerator:

(a/b)/(c/b) = a/c

(a/b)/(a/c) = c/b

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If the result of addition or subtraction is to be expressed using a single denominator, then the operands must have a common denominator before they can be combined. That denominator can be developed "on the fly" using a suitable formula for the sum or difference, but it is required, nonetheless.

(a/b) ± (c/d) = (ad ± bc)/(bd)

This formula is equivalent to converting each operand to a common denominator prior to addition/subtraction:

`(a)/(b)\pm(c)/(d)=(ad)/(bd)\pm(bc)/(bd)=(ad\pm bc)/(bd)`

Note that the denominator 'bd' in this case will not be the "least common denominator" if 'b' and 'd' have common factors. Even use of the "least common denominator" is no guarantee that the resulting rational expression will not have factors common to the numerator and denominator.

For example, ...

5/6 - 1/3 = 5/6 -2/6 = 3/6 = 1/2

The least common denominator is 6, but the difference 3/6 can still be reduced to lower terms.

If we were to use the above difference formula, we would get ...

5/6 -1/3 = (15 -6)/18 = 9/18 = 1/2