 # Rational Expressions Finding LCD Algebra Review: Adding Fractions You can only add like to like Same Denominators.

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Rational Expressions Finding LCD Algebra

Review: Adding Fractions You can only add like to like Same Denominators

Different Denominators Make them the same find a common denominator The product of all denominators is always a common denominator But not always the least common denominator

Finding the LCD Example:

Factor the Denominators

Assemble LCD Each factor in the denominators needs to be used at least once in the LCD.

Build up Fractions to LCD ×5 ×4

Add Numerators And Reduce if Needed

Rational Expressions Example:

Factor the Denominators

Assemble LCD DENOMINATORS Each factor in the denominators needs to be used at least once in the LCD.

Build up Fractions to LCD LCDxxx  ()( )111 x  ()1 x  ()1)(x  ()1 x  ()1 FACTORED DENOMINATORS

Simplify Numerator

Summary of Steps 1.Factor denominators 2.Assemble LCD 3.Build up Fractions 4.Add/Subtract Numerators 5.Simplify Numerator 6.Reduce Factors if Possible

Add or subtract as indicated. So the LCD is 2(x + 3)(x – 3)

Subtract So the LCD is (x – 2)(x + 3)(x – 3)

15. Solve each of the following equations.

Adding and Subtracting Simple Fractions 6-7Page 354

LCDs for Rational Expressions

Rational Expressions