GeminiHeat wrote:
If \(x^3 < 16x\), which of the following CANNOT be true?
(A) \(|x| > 4\)
(B) \(x > −4\)
(C) \(x < −4\)
(D) \(x > 4\)
(E) \(x < 4\)
Testing values is a quick and effective approach...
If x³ < 16x, then it COULD be the case that x = -5, since (-5)³ = -125, 16(-5) = -80, and -125 < -80
Since x can equal -5, we can eliminate answer choices A, C and E, since they all state that x CAN equal -5
Similarly, x³ < 16x, then it COULD be the case that x = 1, since 1³ = 1, 16(1) = 16, and 1 < 16
Since x can equal 1, we can eliminate answer choice B since it states that x CAN equal 1
By the process of elimination, the correct answer is D
In other words, x CANNOT be greater than 4.