Question

Real numbers a,b,c, and d satisfy property ab = 2cd. Which number can not be expressed as the product abcd?

Answer 1

Answer:

As long as your question is about Real Numbers and not whole numbers, the answer is “almost any”.

There are a few restrictions. If either a or b is zero then c or d must be zero as well.

But if a and b are non-zero then they can be any other real numbers you choose. And then c or d can be anything non-zero as well.

If you have chosen a, b and c then d can be calculated by the simple formula  d=ab/2c .

And finally any real number can be expressed as abcd and in an uncountable infinity of ways.