Question

If j and k are nonzero integers, which pair of points must lie in the same quadrant?

(j, j) and (k, k)
(j, k) and (jk, jk)
(j + k, 3) and (3, j + k)
(3j, 3k) and (StartFraction 3 Over j EndFraction, StartFraction 3 Over k EndFraction)

Answer 1

D

Explanation:

Answer 2

Answer: Choice D. (3j, 3k) and (3/j, 3/k)

The slash indicates a fraction.

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Proof:

We'll need to consider 4 different cases.

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Case (1): j > 0 and k > 0

If j > 0, then 3j > 0 and 3/j > 0

If k > 0, then 3k > 0 and 3/k > 0

The two points (3j, 3k) and (3/j, 3/k) are both in quadrant 1.

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Case (2): j > 0 and k < 0

If j > 0, then 3j > 0 and 3/j > 0

If k < 0, then 3k < 0 and 3/k < 0

Points (3j, 3k) and (3/j, 3/k) are both in quadrant 4.

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Case (3): j < 0 and k > 0

If j < 0, then 3j < 0 and 3/j < 0

If k > 0, then 3k > 0 and 3/k > 0

Points (3j, 3k) and (3/j, 3/k) are in quadrant 3.

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Case (4): j < 0 and k < 0

If j < 0, then 3j < 0 and 3/j < 0

If k < 0, then 3k < 0 and 3/k < 0

Points (3j, 3k) and (3/j, 3/k) are in quadrant 4.

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For nonzero integers j and k, we've shown that Points (3j, 3k) and (3/j, 3/k) are in the same quadrant. This concludes the proof.