Yes, it can be expressed as a ratio of two integers: -1086 / 10 or -543/5
Yes, the product of two rational numbers is always a rational number.
Yes. Rational functions must contain rational expressions in order to be rational.
No. For example, 20.5 is irrational; indeed it was one of the first irrational numbers to be discovered.
Sure. Let's take an example with numbers instead of variables. 8/9 is a rational number - the ratio of two integers. If you square it, you get (8/9)2 = 82/92 = 64/81; that is, if you square each...