13 Addition and Subtraction: Like Denominators

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13 Addition and Subtraction Like Denominators

• 1/27/09

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Warm up

• 1 3
• 5 5

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How do we add?

• Simply write the sum or difference over the
  common denominator
• Factor and simplify when appropriate

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Warning

• Mistakes are easily made in subtraction!
• Use parentheses when subtracting!

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Example

• x2 4x 10 x 18
• x 7 x - 7

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Example 2

• 4m 5 - 2m 1
• m 1 m - 1

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Example 3

• 5x2 3x 2 - 3x2 3x 2
• 2x 1 2x - 1

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13 Addition and Subtraction Unlike Denominators

• 1/27/09

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Warm up

• Add the following
• 1 2
• 5 7
• 1(7) 2(5) 710 17
• 5(7) 7 (5) 35 35

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Adding Rational Expressions

• When adding rational expressions, we use the
  general formula

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Examples

• 2x 6
• 3 x
• x 4 _
• x 2 x 2