07-11-2016, 10:29 PM
(This post was last modified: 07-11-2016, 10:45 PM by Karadoborgu.)
A) Is wrong, because any positive real number divided by negative will never be positive.
B) Is wrong. Absolute value of negative number turns it to positive. So there are pairs of x and y which destroy this equality. For example 2*2 > |-100| => 4 > 100, not true
C) Is right. You can simplify everything to x>y and a positive number is always bigger than negative one
D) Is wrong. Simplifies to x*x > y*y. Can't be true because y can be bigger than x and the other way around
E) is the same as D. You can multiply both sides by y*y ( positive number, wont change equality sign) and multiply by x*x and you get y*y > x*x
B) Is wrong. Absolute value of negative number turns it to positive. So there are pairs of x and y which destroy this equality. For example 2*2 > |-100| => 4 > 100, not true
C) Is right. You can simplify everything to x>y and a positive number is always bigger than negative one
D) Is wrong. Simplifies to x*x > y*y. Can't be true because y can be bigger than x and the other way around
E) is the same as D. You can multiply both sides by y*y ( positive number, wont change equality sign) and multiply by x*x and you get y*y > x*x