Find all real numbers for which the rational expression is undefined. (enter your answers as a comma-separated list. if no values make the expression undefined, enter none.) 6x-19/x2 - 81

+9, -9

Step-by-step explanation: The rational expression in this case is undefined if the the denominator is equal to zero, which means that the x cannot be whatever makes the denominator zero, so:

x² - 81 = 0 ⇒ x² = 81 ⇒ x = +/- √81 ⇒ x = +/- 9

Note that we are using the equal sign just because this particular problem askes for a solutions that is undefined.

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