paddy41 wrote:

If x and y are negative and \(x^4-y^4<0\) which of the following must be true?

I: \(x<y\)

II: \(xy<y^2\)

III: \((x+y)^2<(x-y)^2\)

A.) I only

B.) II only

C.) III only

D.) I & II

E.) II & III

From question stem, We can organize exmaples

Let x = -1 & y = -2

Let x = \(\frac{-1}{4}\) & y = \(\frac{-1}{2}\)

Let x = \(\frac{-1}{2}\) & y = -1

I: \(x<y\)........From examples above..........

NOT TrueII: \(xy<y^2\)....\(xy-y^2<0\).......y<0 & x>y........From examples above........

TrueIII: \((x+y)^2<(x-y)^2\)..........Take first example to DISPROVE........

NOT TrueAnswer: B