#2 is quite simple . . .
2. Prove that: .if , then:
We are given: . .
. . Hence, both and are positive.
Divide  by the positive quantity
for this proof, it is assumed you know basic properties of numbers. in particular, that the product of two negative numbers is positive.
Assume and . Then . Therefore we must have , since this is the product of two negative numbers. Thus we have , as desired.