1. Rational Expressions To add or subtract rational expressions, find the least common denominator, rewrite all terms with the LCD as the new denominator, then combine like terms. To multiply rational expressions (fractions), multiply the numerators, and multiply the denominators. To divide rational expressions, invert the second expression and then follow the rules for multiplication. If possible, it may be helpful to factor the numerators and denominators before multiplying.

2. Rational Equations To solve rational equations, multiply both sides of the equation by the LCD of both sides of the equation, and then solve. Be sure to check your answers by substituting them back into the original equation, in case your solution causes the original expression to become undefined (a zero in the denominator).