Find the value of the variable that makes rational expression undefined. 3x/x-3

X cannot equal to zero. So if you substitute 3 it’ll make 3-3 which equals to 0. If you divide in a fraction anything by zero the answer will be undefined. So 3x/0 is undefined. So the value that you are looking for is 3. Remember if you have a fraction, the bottom (denominator) cannot be 0. You can’t divide the top by zero. In your calculator it’ll either say error or undefined

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