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If a^2+2ab+b^2
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11 Jan 2021, 21:54
11 Jan 2021, 21:54
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Question Stats:
100% (01:16) correct
0% (00:00) wrong based on 3 sessions
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If \(a^2+2ab+b^2=9\), then \((2a+2b)^3=\)
A. 3
B. 6
C. 9
D. 27
E. 216
Kudos for the right answer and explanation
A. 3
B. 6
C. 9
D. 27
E. 216
Kudos for the right answer and explanation
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Given Kudos: 136
If a^2+2ab+b^2
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12 Jan 2021, 06:44
12 Jan 2021, 06:44
1
Carcass wrote:
If \(a^2+2ab+b^2=9\), then \((2a+2b)^3=\)
A. 3
B. 6
C. 9
D. 27
E. 216
Kudos for the right answer and explanation
A. 3
B. 6
C. 9
D. 27
E. 216
Kudos for the right answer and explanation
I'm not crazy about this question. Here's why:
Take: \(a^2+2ab+b^2=9\)
Factor to get: \((a+b)(a+b)=9\)
In other words: \((a+b)^2=9\)
So, EITHER \((a+b)=3\) OR \((a+b)=-3\)
If \((a+b)=3\), then \((2a+2b)^3=[2(a+b)]^3=[2(3)]^3=6^3=216\).
Answer: E
If \((a+b)=-3\), then \((2a+2b)^3=[2(a+b)]^3=[2(-3)]^3=(-6)^3=-216\)
Since \(-216\) is not among the answer choices, the question should read something like: "If \(a^2+2ab+b^2=9\), then \((2a+2b)^3\) COULD equal"
Cheers,
Brent
gmatclubot
If a^2+2ab+b^2 [#permalink]
12 Jan 2021, 06:44
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