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25 Jun 2012, 11:57
Kudos
Bookmarks
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
64% (01:32) correct
36%
(01:32)
wrong
based on 152
sessions
History
Date
Time
Result
Not Attempted Yet
What does p equal?
(1) \(2p^2=p^3\)
(2) \(p=2\sqrt{p-1}\)
i went with D, but was wrong
(1) 2p^2=p^3 divided by p^2 --> 2=p - here was the mistake and id like to ask you to shed the light on this - what don't i understand correctly here?
(1) \(2p^2=p^3\)
(2) \(p=2\sqrt{p-1}\)
i went with D, but was wrong
(1) 2p^2=p^3 divided by p^2 --> 2=p - here was the mistake and id like to ask you to shed the light on this - what don't i understand correctly here?
25 Jun 2012, 12:07
Kudos
Bookmarks
Galiya
What does p equal?
(1) 2p^2=p^3 --> \(p^3-2p^2=0\) --> \(p^2(p-2)=0\) --> \(p=0\) or \(p=2\). Not sufficient.
(2) \(p=2\sqrt{p-1}\) --> \(p^2=4(p-1)\) --> \(p^2-4p+4=0\) --> \((p-2)^2=0\) --> \(p=2\). Sufficient.
Answer: B.
As for your solution: you cannot divide by \(p^2\) since \(p\) could be zero and division by zero is not allowed.
Never reduce equation by variable (or expression with variable), if you are not certain that variable (or expression with variable) doesn't equal to zero. We can not divide by zero. So, if you divide (reduce) by \(p^2\) you assume, with no ground for it, that \(p\) does not equal to zero thus exclude a possible solution.
Hope it's clear.
