What causes a solution to a rational equation to be an extraneous solution? When there is more than one solution, one of the solutions is extraneous
If a solution/results in zero when substituted into the denominator of the equation, the solution is extraneous
If a solution results in a negative number when substituted into the denominator of the equation the solution
extraneous
When a solution is a fraction, the solution is extraneous.

This is a rational expression because the denominator contains a variable. this is a polynomial with 3 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 4 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 4 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 3 terms. this is a rational expression because the denominator contains a variable. this is a polynomial with 5 terms.