SajjadAhmad wrote:
If \((x^3+y^6)\) is positive, which of the following must be true?
A. \(x\) is positive
B. y is positive
C. \(x^3\) is negative
D. \((x+y^2)\) and \((x^2+y^4−xy^2)\) are either both positive or both negative
E. \(∣x^3∣ < y^6\)
Source: Manhattan Review
Since the given expression can be factored as (x + y^2)(x^2 + y^4 - xy^2), we see that those factors must be either both positive or both negative.
Answer: D
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