Question

Prove the sum of two rational numbers is rational where a, b, c, and d are integers and b and d cannot be zero.

Answer 1

Step-by-step explanation:

just look what happened :

every term was multiplied by a factor with the value 1 (to keep the original value) but to establish a common denominator.

a/b was multiplied by d/d, and c/d was multiplied by b/b, so that the common denominator is then bd.

so, the first answer option is correct.

although I am a bit unhappy with its phrasing.

but the other options are definitely wrong.