SOLUTION: <pre><b><font size = 3>Find the real number for which this rational expression is undefined: 5x+9 ----------- 4x²-4x-15</pre>

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Question 31141This question is from textbook Intro Algebra
: 
Find the real number for which this rational expression is undefined:

   5x+9
-----------
 4x²-4x-15

 This question is from textbook Intro Algebra

Answer by AnlytcPhil(1806)   (Show Source): You can put this solution on YOUR website!
Find the real number for which each rational expression is 
undefined.

    5x+9
 -----------
  4x²-4x-15

A rational expression is undefined if its denominator is 0.

So set the denominator = 0 and solve for x.

 denominator = 4x² - 4x - 15 = 0

The left side factors as

            (2x + 3)(2x - 5) = 0

Use to zero-factor principle.  Set each factor = 0 and solve:

Setting 2x + 3 = 0 gives x = -3/2
Setting 2x - 5 = 0 gives x = 5/2

Therefore the expression is undefined for x = -3/2 or 5/2

Edwin
AnlytcPhil@aol.com
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