It is always FALSE.
Yes
Yes. For example, if you multiply the square root of 2 (an irrational number) by itself, the answer is 2 (a rational number). The golden ratio (Phi, approx. 1.618) multiplied by (1/Phi) (both irrational numbers) equals 1 (rational). However, this is not necessarily true for all irrational numbers.
Well, darling, when you add two irrational numbers together, they can sometimes magically cancel each other out in such a way that the sum ends up being a rational number. It's like mixing oil and water and somehow getting a delicious vinaigrette. Math can be a wild ride, honey.
This can't be proved because it is not necessarily true. If x is 2 and y is 1 then x-y is 1, which is rational. The product of 2x and 3y is 12, which is also rational. Sadly, you can't disprove it either; for certain values of x,y it is true as posited.
Yes, that's true.
The product of 2 rationals must be rational. The product of a rational and an irrational is irrational (unless the rational is 0) The product of two irrationals can be either rational or irrational.
It is always true.
It is true.
Yes
Yes. For example, if you multiply the square root of 2 (an irrational number) by itself, the answer is 2 (a rational number). The golden ratio (Phi, approx. 1.618) multiplied by (1/Phi) (both irrational numbers) equals 1 (rational). However, this is not necessarily true for all irrational numbers.
True.
In between any two rational numbers there is an irrational number. In between any two irrational numbers there is a rational number.
In between any two rational numbers there is an irrational number. In between any two Irrational Numbers there is a rational number.
Any and every rational number.
Only if the negative sign is associated with an even root. In that case, the number is neither rational nor irrational, but is imaginary.
yes
Let your sum be a + b = c, where "a" is irrational, "b" is rational, and "c" may be either (that's what we want to find out). In this case, c - b = a. If we assume that c is rational, you would have: a rational number minus a rational number is an irrational number, which can't be true (both addition and subtraction are closed in the set of rational numbers). Therefore, we have a contradiction with the assumption that "c" (the sum in the original equation) is rational.