#### Answer

not one-to-one

#### Work Step by Step

See p.407, Horizontal Line Test
A function is one-to-one if every horizontal line intersects the graph of the function at most once.
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We find many horizontal lines that intersect the graph more than once.
One line is enough to fail the test. so we take the x-axis ($y=0)$.
Horizontal Line Test: FAIL.
The function is not one-to-one.