When would there be only four different equations for a set of math mountain numbers give an example

He that is measured at 220° is a reflex angle. the opposite angle is obtuse. find the measure of obtuse .

Is the product of two rational numbers irrational or rational? first, make a hypothesis by multiplying two rational numbers. then, use variables such as x=a/b and y=c/d and the closure property of integers to prove your hypothesis.

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?