Excluded from the domain

Which value(s) must be excluded as a value of x in the polynomial?

   x - 2
--------
  x² - 25

The domain is the set of x values or “inputs”.

You cannot have a denominator equal to 0, that would be "undefined",
because you cannot divide by 0.

To find the numbers to be excluded, find the numbers that make the denominator equal to 0, by setting the denominator equal to 0.

  x - 2
--------
 x² - 25

x² - 25 = 0   {set denominator equal to 0}
x² = 25   {added 25 to both sides}
x = 5 or -5   {took square root of both sides}

x cannot be 5 or -5

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