Undefined Expressions
An expression is undefined any time the denominator is equal to 0.
An expression is undefined any time the denominator is equal to 0.
Add or subtract the coefficients of terms that have the same variable. Remember the sign stays with the number that comes after it.



Multiply the expression outside the parentheses times every term inside the parentheses. Watch for the minus sign. This is one of the most common sign errors!


