Prove the sum of two rational numbers is rational where a, b, c, and d are integers and b and d cannot be zero. Steps Reasons 1. a over b plus c over d Given 2. ad over bd plus cb over bd 3. ad plus cb all over bd Simplify Fill in the missing reason in the proof. Multiply to get a common denominator. Add to get a common denominator. Distribute d to all terms. Add d to all terms.