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 Depdendent Variable

 Number of equations to solve: 23456789
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 Dependent Variable

 Number of inequalities to solve: 23456789
 Ineq. #1:
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# Adding and Subtracting Rational Expressions With Unlike Denominators

After studying this lesson, you will be able to:

Add and subtract rational expressions with unlike denominators.

• Remember that when we add or subtract fractions, we must have a common denominator before we can add. The same is true for adding and subtracting rational expressions.
• Once we have a common denominator, we keep the denominator and we add the numerators. Collect like terms in the numerator.
• Next, simplify if possible by factoring, canceling, and/or reducing.

Example 1

Find the lowest common denominator for the set of expressions or numbers: 4, 10, 20

20 will be the lowest common denominator

Example 2

Find a common denominator for the set of expressions or numbers: 3, 15, 21

105 will be the lowest common denominator

Example 3

Find a common denominator for the set of expressions or numbers: x 2, x 3, x 4

to find the lowest common denominator for variables, we use the highest power of the variable

x 4 will be the lowest common denominator

Example 4

Find a common denominator for the set of expressions or numbers: y, y 2, y 3

to find the lowest common denominator for variables, we use the highest power of the variable

y 3 will be the lowest common denominator

Example 5

Find a common denominator for the set of expressions or numbers: 12x 2 , 20x 2

60x 2 will be the lowest common denominator

Example 6

Find a common denominator for the set of expressions or numbers: 5x 3, 10x 4, 15x 2,

30x 4 will be the lowest common denominator