Real numbers x, y, and z satisfy the inequalities 0<x<1, −1<y<0, and 1<z<2. Which of the following numbers is necessarily positive?
Pick one
Solution
Notice that y+z must be positive because ∣z∣>∣y∣. Therefore the answer is (E) y+z. The other choices: (A) As x grows closer to 0, x2 decreases and thus becomes less than y. (B)x can be as small as possible (x>0), so xz grows close to 0 as x approaches 0. (C) For all −1∣y2∣, and thus it is always negative. (D) The same logic as above, but when −21<y<0 this time.
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