how do I determine if a function is one-to-one?

Question

blurbendy · Answer

Basically if each value in the domain maps to a unique value in the range (i.e. if 1 and 2 are in the domain, they both can't map to 5).

blurbendy · Answer

actually that would be codomain, not range

anonymous · Answer

okay for example..  f(x) = x^2 +2x -4
how would I know?

amistre64 · Answer

if you can draw it, use a "horizontal" line test

anonymous · Answer

You would do the horizontal line test.

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The first one is not a one to one function because when you do the horizontal line test it touches more than one point on the graph.

The second one is one to one function because when you do the horizontal line test it touches the graph in only one place.