<PRE><B>Question 537977</B>
The expression is undefined when the denominator is 0.&lt;P&gt;
{{{(z^2)-4z-5=0}}}&lt;P&gt;
Factor it:&lt;P&gt;
{{{(z+1)(z-5)=0}}}&lt;P&gt;
Set each = 0 to find the x-value that makes it 0.&lt;P&gt;
z+1 = 0 &lt;P&gt;
Subtract 1 from both sides.&lt;P&gt;
z=-1&lt;P&gt;
z-5=0&lt;P&gt;
Add 5 to both sides.&lt;P&gt;
z=5&lt;P&gt;
The expression is undefined when z=-1 and when z=5.

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