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What is the value of a^3+b^3-c^3+3abc/a^2+b^2+c^2+ac+bc-ab

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What is the value of a^3+b^3-c^3+3abc/a^2+b^2+c^2+ac+bc-ab  [#permalink]

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New post 24 Jan 2012, 09:59
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A
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  45% (medium)

Question Stats:

69% (02:05) correct 31% (02:17) wrong based on 142 sessions

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What is the value of \(\frac{a^3+b^3-c^3+3abc}{a^2+b^2+c^2+ac+bc-ab}\)?

A. a+b-c
B. a-b+c
C. -a+b+c
D. a-b-c
E. -a+b-c
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What is the value of a^3+b^3-c^3+3abc/a^2+b^2+c^2+ac+bc-ab  [#permalink]

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New post 14 Jul 2014, 22:38
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\(\frac{a^3+b^3-c^3+3abc}{a^2+b^2+c^2+ac+bc-ab}\)

This also means that \(a^2+b^2+c^2+ac+bc-ab\) when multiplied with any one of the 5 options, gives answer \(a^3+b^3-c^3+3abc\)

Just focus on \(a^2, b^2, c^2\) in the LHS & \(a^3+b^3-c^3\) on RHS

\(a^2\) has to be multiplied by "a" to give \(a^3\)

Similarly,\(b^{2} * b = b^3\)

\(c^{2} * -c = -c^3\)

Answer = a+b-c

Answer = A
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Re: Simplest form of expression  [#permalink]

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New post 24 Jan 2012, 11:26
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LM wrote:
What is the value of \(\frac{a^3+b^3-c^3+3abc}{a^2+b^2+c^2+ac+bc-ab}?\)

A) a+b-c

B) a-b+c

C) -a+b+c

D) a-b-c

E) -a+b-c


Plug-in method would be the most efficient way to deal with this problem.

Let \(a=2\), \(b=1\) and \(c=0\). Then \(\frac{a^3+b^3-c^3+3abc}{a^2+b^2+c^2+ac+bc-ab}=3\). Now let's see which answer choice yields 3:

A. a+b-c=3 --> correct;
B. a-b+c=1 --> discard;
C. -a+b+c=-1 --> discard;
D. a-b-c=1 --> discard;
E. -a+b-c=-1 --> discard.

Answer: A.

P.S. For plug-in method it might happen that for some particular numbers more than one option may give "correct" answer. In this case just pick some other numbers and check again these "correct" options only.

Hope it helps.
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Re: What is the value of a^3+b^3-c^3+3abc/a^2+b^2+c^2+ac+bc-ab  [#permalink]

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New post 01 Dec 2018, 10:17
PareshGmat wrote:
\(\frac{a^3+b^3-c^3+3abc}{a^2+b^2+c^2+ac+bc-ab}\)

This also means that \(a^2+b^2+c^2+ac+bc-ab\) when multiplied with any one of the 5 options, gives answer \(a^3+b^3-c^3+3abc\)

Just focus on \(a^2, b^2, c^2\) in the LHS & \(a^3+b^3-c^3\) on RHS

\(a^2\) has to be multiplied by "a" to give \(a^3\)

Similarly,\(b^{2} * b = b^3\)

\(c^{2} * -c = -c^3\)

Answer = a+b-c

Answer = A


This is such a smart and "simple" approach, kudos mate!
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Re: What is the value of a^3+b^3-c^3+3abc/a^2+b^2+c^2+ac+bc-ab   [#permalink] 01 Dec 2018, 10:17
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