SOLUTION: Find all numbers for which the rational expression is undefined. z^2+20 ------ z^2-4z-5 thats a fraction.

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: Find all numbers for which the rational expression is undefined. z^2+20 ------ z^2-4z-5 thats a fraction.       Log On


   



Question 537977: Find all numbers for which the rational expression is undefined.
z^2+20
------
z^2-4z-5
thats a fraction.

Answer by fcabanski(1391) About Me  (Show Source):
You can put this solution on YOUR website!
The expression is undefined when the denominator is 0.


%28z%5E2%29-4z-5=0


Factor it:


%28z%2B1%29%28z-5%29=0


Set each = 0 to find the x-value that makes it 0.


z+1 = 0


Subtract 1 from both sides.


z=-1


z-5=0


Add 5 to both sides.


z=5


The expression is undefined when z=-1 and when z=5.

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