Math help can anyone show you how to do this please Prove or disprove that if a and b are rational number then ab is rational?

Answer 1

To prove a number ab is rational, you have to find two integers t and n such that t/n = ab.

Since we know that a, and b are rational, they can be expressed as follows:

a = p1/q1
b = p2/q2

then ab = p1p2/q1q2

Since p1, p2, q1, and q2 are all integers, p1p2 is an integer, and q1q2 is an integer. This gives us the t, and n we are looking for. t = p1p2 and n = q1q2, and ab = t/n, so ab is rational.