Which of the following must be non-negative?
A. (a-0.9)(a-1)
B. (a+1)(a-1)
C. (a+0.9)(a+1)
D. (a-0.9)(a-0.9)
E. a(a+1)
OA D
Source: Economist GMAT
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Which of the following must be non-negative?
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D: (a-0.9)(a-0.9) = (a-0.9)².BTGmoderatorDC wrote:Which of the following must be non-negative?
A. (a-0.9)(a-1)
B. (a+1)(a-1)
C. (a+0.9)(a+1)
D. (a-0.9)(a-0.9)
E. a(a+1)
The square of a value cannot be negative.
The correct answer is D.
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Since a perfect square is always non-negative, we see that (a - 0.9)(a - 0.9) = (a - 0.9)^2 is always non-negative.BTGmoderatorDC wrote:Which of the following must be non-negative?
A. (a-0.9)(a-1)
B. (a+1)(a-1)
C. (a+0.9)(a+1)
D. (a-0.9)(a-0.9)
E. a(a+1)
OA D
Source: Economist GMAT
Answer: D
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