Is a^2 > 3a - b^4?
(1) 3a - b^4 = -5
(2) a > 5 and b > 0
OA D
Source: Veritas Prep
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Is a^2 > 3a – b^4?
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BTGmoderatorDC
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Jay@ManhattanReview
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Let's take each statement one by one.BTGmoderatorDC wrote:Is a^2 > 3a - b^4?
(1) 3a - b^4 = -5
(2) a > 5 and b > 0
OA D
Source: Veritas Prep
(1) 3a - b^4 = -5
=> The question rephrased to: Is a^2 > -5?
Since a^2 is a non-negative number, a^2 > -5. Sufficient.
(2) a > 5 and b > 0
We have: Is a^2 > 3a - b^4?
=> a^2 -3a > -b^4
=> a(a - 3) > -b^4
Since a > 5, we have (a - 3) > 2
Thus, a(a - 3) is positive.
Since given b > 0, we have b^4 is a positive number.
Thus, -b^4 is a negative number.
=> a(a - 3) > -b^4. Sufficient.
The correct answer: D
Hope this helps!
-Jay
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