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If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) =

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Kudos [?]: 129061 [0], given: 12190

If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) = [#permalink]

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New post 05 Sep 2017, 01:27
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A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

85% (01:19) correct 15% (02:48) wrong based on 45 sessions

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Kudos [?]: 129061 [0], given: 12190

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If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) = [#permalink]

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New post 05 Sep 2017, 01:30
We have been asked to find the value for \(a(4a + 1) = 4a^2 + a\).

\(2a^2 + 0.5a - 1 = 0\) when multiplied by 2, gives \(4a^2 + a - 2 = 0\)
Hence, the expression \(4a^2 + a - 2 = 0\) can be re-written as \(4a^2 + a = 2\)(Option B)
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Re: If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) = [#permalink]

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New post 05 Sep 2017, 01:31
Bunuel wrote:
If \(2a^2 + 0.5a - 1 = 0\), then \(a(4a + 1) =\)

A. 0.5
B. 2
C. 3.5
D. 4
E. 0


- \(2a^2 +0.5a - 1 = 0\), we can get rid of decimal by multiply by 2 -> \(4a^2 + a - 2 = 0\).
- We can add both sides with 2 -> \(4a^2 + a = 2\) -> \(4a^2 + a = -2\) -> \(a(4a+1) = 2\).

B.
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Re: If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) = [#permalink]

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New post 07 Sep 2017, 16:47
Bunuel wrote:
If \(2a^2 + 0.5a - 1 = 0\), then \(a(4a + 1) =\)

A. 0.5
B. 2
C. 3.5
D. 4
E. 0


2a^2 + 0.5a - 1 = 0

4a^2 + a - 2 = 0

4a^2 + a = 2

a(4a + 1) = 2

Answer: B
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Kudos [?]: 845 [0], given: 3

Re: If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) =   [#permalink] 07 Sep 2017, 16:47
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If 2a^2 + 0.5a - 1 = 0, then a(4a + 1) =

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