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Question Stats:
64% (01:18) correct
35% (01:50) wrong based on 87 sessions
What is the value of p^3 - q^3 ? 1. p - q = 0 2. p + q = 0 DS Question, I don't buy the answer. I answered D. Reasoning: p^3 - q^3 = (p - q) (p + q) (p - q) statement 1: (p-q) = 0, then p^3 - q^3 = 0 statement 2: (p+q) = 0, then p^3 - q^3 = 0 Am I missing something?OE: From statement (1) it is clear that p=q , so the initial difference is 0. Absolutely enough. Statement (2) doesn't give any additional information. So, the answer is A.
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I think what you're missing is this: In #2, q = -p, or the opposite of p. So p + q = 0, then if p = 2, then q = -2. So that 2 + -2 = 0. Works. Now apply this to p^3 - q^3First try p = 2 and q = -2: 2^3 - (-2)^3 = 8 - - 8 = 16Now try p = -2 and q = 2: (-2)^3 - 2^3 = -8 - 8 = -16In both situations, p + q = 0, but when used in the equation given in the stem, we get different values so the statement cannot be sufficient, and therefore, A must be the answer since B is insufficient. x-ALI-x wrote: DS Question, I don't buy the answer.
Question:
What is the value of p^3 - q^3 ?
1. p - q = 0
2. p + q = 0
I answered D. Reasoning:
p^3 - q^3 = (p - q) (p + q) (p - q)
statement 1: (p-q) = 0, then p^3 - q^3 = 0
statement 2: (p+q) = 0, then p^3 - q^3 = 0
Am I missing something?
OA is A.
OE: From statement (1) it is clear that p=q , so the initial difference is 0. Absolutely enough. Statement (2) doesn't give any additional information. So, the answer is A
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Manager
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Thanks JAllen. You're absolutely right. The way I solved it is off. Thanks for the correction
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x-ALI-x wrote: DS Question, I don't buy the answer.
Question: What is the value of p^3 - q^3 ?
1. p - q = 0
2. p + q = 0
I answered D. Reasoning:
p^3 - q^3 = (p - q) (p + q) (p - q)
statement 1: (p-q) = 0, then p^3 - q^3 = 0
statement 2: (p+q) = 0, then p^3 - q^3 = 0
Am I missing something?
OA is A.
OE: From statement (1) it is clear that p=q , so the initial difference is 0. Absolutely enough. Statement (2) doesn't give any additional information. So, the answer is A In fact, you got incorrect formula for p^3 - q^3. it is: p^3 − q^3 = (p−q)(p^2 + pq + q^2) A should be OA.
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xALIx wrote: What is the value of p^3 - q^3 ? 1. p - q = 0 2. p + q = 0 DS Question, I don't buy the answer. I answered D. Reasoning: p^3 - q^3 = (p - q) (p + q) (p - q) statement 1: (p-q) = 0, then p^3 - q^3 = 0 statement 2: (p+q) = 0, then p^3 - q^3 = 0 Am I missing something?OA is A. OE: From statement (1) it is clear that p=q , so the initial difference is 0. Absolutely enough. Statement (2) doesn't give any additional information. So, the answer is A. Its A. p^3 - q^3 = (p-q)(p^2+q^2+pq) hence 1 is enough.
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(p-q)^3=p^3-q^3-3pq(p-q)p^3-q^3=(p-q)^3+3pq(p-q)case 1. p-q =0p^3-q^3=(0)^3+3pq(0)p^3-q^3=(0)case 2. p+q=0 implies p=-qp^3-q^3=(-q-q)^3+3(-q)q(-q-q)p^3-q^3=-8q^3+6q^3p^3-q^3=-2q^3 (which is dependent on value of q : insufficient) Seems A is right
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p^3 -q^3 = (p-q)(p^2+pq+q^2) Case 1: If p-q=0 The value of p^3 -q^3=0  => Stmt 1 is suff. (A/D can be option) Case 2: if p+q=0 The value is in terms of p or q which is we still have one variable which is not definite value. =>stmt is not suff. (D can't be option) OA is A.
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Hope my approach is correct anyway. (1) p-q=0 => p = q. So, p^3 - q^3 = 0 (since p=q) Sufficient. (2) p+q = 0; => p = -q. So, p^3 - q^3 results: 2p^3 or -2q^3. We don't know the values of p and q; Insufficient
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Ans : A from S1=we can say P=Q so for all Ans is 0
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Option A is answer.
Formulae for p^3 − q^3 = (p-q)(p^2+pq+q^2)
Option 1 is enough.
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stmt 1: p-q=0 so, p=q i.e. p^3=q^3So, P^3-q^3=0smt 2: p+q=0. Can't say anything from here So answer is A
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X^3+Y^3=(X+Y)*(X^2-XY+Y^2)X^3-Y^3=(X-Y)*(X^2+XY+Y^2)
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(1) p = q p^3 - q^3 = 0 Sufficient (2) p+q = 0 Not sufficient p = q = 0 => p^3 - q^3 = 0 p = 1, q = -1 => 1 - (-1) = 2 Answer - A
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BELOW ALGEBRAIC FORMULA'S CAN BE USED
1. a^3 − b^3 = (a−b)(a^2 + ab + b^2)
2. a^3 + b^3 = (a+b)(a^2 − ab + b^2)
3.a^3 − b^3 = (a−b)^3 + 3ab(a − b)
STATEMENT 1 IS SUFFICIENT.
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xALIx wrote: What is the value of p^3 - q^3 ? 1. p - q = 0 2. p + q = 0 DS Question, I don't buy the answer. I answered D. Reasoning: p^3 - q^3 = (p - q) (p + q) (p - q) statement 1: (p-q) = 0, then p^3 - q^3 = 0 statement 2: (p+q) = 0, then p^3 - q^3 = 0 Am I missing something?OA is A. OE: From statement (1) it is clear that p=q , so the initial difference is 0. Absolutely enough. Statement (2) doesn't give any additional information. So, the answer is A. Yes you are missing something and that is the correct factorization of p^3 - q^3 which is (p-q)*(p^2+p*q+q^2). And as the p+q is not a factor we won't be able to get an answer based on p+q=0 so st2 is insufficient.
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AM
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1. Sufficient . As expression becomes 0. 2. Not sufficient . We don't know the value of q. Answer is A. Posted from my mobile device 
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I got it wrong but the OA is A
as statement 1 implies that |p| = |q| and they are of same sign or p and q both are zero, then only statement 1 holds good.
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what level is this question?
looks more like a 500-600 type question....
straightforward (A)
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p³ – q³ = (p – q)(p² + pq + q²)
you know thpt
(p – q)³ = p³ + 3pq(p – q) – q³
then p³ – q³ = (p – q)³ + 3pq(p – q)
= (p – q)[(p – q)² + 3pq]
= (p – q)(p² – 2pq + q² + 3pq)
= (p – q)(p² + pq + q² )
Choice 1 is sufficient to conclude that p³ – q³ =0 as p-q =0
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