We see a yes/no inequality question with variables. We think: be careful about multiplying or dividing both sides by a variable - if the variable could be negative, weird things may happen!HSPA wrote:Is 1/p > r/(r^2 + 2) ?
(1) p = r
(2) r > 0
(1) we immediately consider p=r=0. In this case, 1/p is undefined, so it's impossible to answer the question: insufficient.
(2) no info about p: insufficient.
Combined: we know that p=r>0, i.e. both p and r are positive. It's now safe to multiply or divide by p and/or q!
Subbing in p=r:
Is 1/r > r/(r^2 + 2)?
Cross multiplying:
Is r^2 + 2 > r^2?
Subtracting r^2 from both sides:
Is 2 > 0?
That's a definite yes - sufficient, choose (C)!
