Rational Expression Calculator

This treats one polynomial over another as a single expression: it cancels the common factor and says which values the variable was never allowed to take. Enter the top and the bottom in separate boxes, or two whole expressions with an operation between them, and it returns the reduced form, both sides factored, the factor that cancelled and the excluded values. Those exclusions come from the original denominator rather than the simplified one, which is the step most often lost when cancelling on paper. It works in one variable with whole-number coefficients up to degree four, all in exact integer arithmetic, so no answer here is rounded.