Notes
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Outline
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Equations
with
Algebraic Fractions
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To Factor Algebraic Fractions
  • a. Factor the denominators
  • b. Find the least common denominator (LCD)
  • c.  Multiply each side of the equation by the LCD
  • d.  Solve for the variable
  • e.  Check for a valid solution by substituting the
  •      result into the original problem.
    • A solution is invalid if the denominator becomes zero.
    • A solution is invalid if the two sides of the equation
    • are not equal.
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Algebraic Fractions Example 1

  •     a.  Factor the denominators
  •                9 = 3 ·3
  •                7 = 7 ·1
  • b.  LCD = 3 ·3 ·7 = 63
  • c.   Multiply each side of the equation by the LCD


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Example 1       page 2
  • d.  Solve for the variable        e.  Check the solution in
  •                                                          the original equation


  •       7x  +  9x  = 63
  •                   16x  = 63
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Algebraic Fractions Example 2
  • a.  Factor the denominators
  •      3 = 3 ·1,      4 = 2 ·2,      2 = 2 · 1
  • b.  LCD = 3 ·2 ·2 = 12
  • c.  Multiply each side of the equation by the LCD
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Example 2       page 2
  •     d.  Solve for the variable         e.  Check the solution in                                            the original equation








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Algebraic Fractions Example 3
  • a.  Factor the denominators
  •      4 = 2 ·2
  •   y + 2      (not factorable)
  • 28 = 2 ·2 ·7
  • b.  LCD = 2 ·2 ·7·(y + 2) = 28 (y + 2)
  • c.  Multiply each side of the equation by the LCD
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Example 3       page 2
  • d.  Solve for the variable         e.  Check the solution in                                   the original equation
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Algebraic Fractions Example 4
  • a.  Factor the denominators
  •      5        (not factorable)
  • 2p-1   (not factorable)
  • b.  LCD = 5(2p-1)
  • c.  Multiply each side of the equation by the LCD
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Example 4       page 2
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Example 4       page 3
  • e.  Check the solutions in the original equation
  •      for                                     for
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Algebraic Fractions Example 5
  • a.  Factor the denominators
  •       r + 2  (not factorable)
  •       r - 5   (not factorable)
  • b.  LCD = (r + 2)(r - 5)
  • c.  Multiply each side of the equation by the LCD
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Example 5       page 2
  • d.  Solve for the variable            e.  Check the solution in
  •                                                          the original equation



  •        Note:  This is the exact form of the
  •                   original equation that would be
  •                   obtained by cross multiplying


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Algebraic Fractions Example 6
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Example 6       page 2
  • d.  Solve for the variable         e. Check the solutions in the     original equation for r = 3



  •                                                                                                   for  r = -1
  •                                                                                                          The denominator becomes zero.
  •                                                                                                          -1 can not be a solution.