A one-to-one function (or injective function) is defined such that each input maps to a unique output; no two different inputs can map to the same output.
Let's analyze the given relations:
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{(−3,−2), (3,4), (−1,−2), (−1,5)}: The input -1 maps to both -2 and 5. Not one-to-one.
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{(1,2), (1,4), (1,5), (1,6)}: The input 1 maps to multiple outputs (2, 4, 5, 6). Not one-to-one.
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{(4,−5), (3,−5), (2,8), (1,8)}: The inputs 4 and 3 both map to -5, and 2 and 1 both map to 8. Not one-to-one.
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{(10,9), (8,7), (6,5), (4,3)}: All inputs map to unique outputs (10 to 9, 8 to 7, 6 to 5, 4 to 3). This is one-to-one.
Conclusion: The relation {(10,9), (8,7), (6,5), (4,3)} is the only one that is a one-to-one function.