Kenneth S. answered • 01/09/17

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y = 2x + 1 or f(x) = 2x + 1 is a function. It's defined for every Real number (that's domain) and in this case the range (all possible output "y" values) is also all Reals.

f(x) = x

^{2}+1 is another function; domain is all Reals but range is y ≥ 1.Finally, {(0,2) (1,3) (5,-1)} is a function; domain is {0,1,5} and range is {-1,2,,3}.

Any of these, when graphed, will pass the Vertical Line Test and therefore qualifies as a function. If ANY vertical line crosses the graph no more than once, it's a function.

Andrew M.

01/09/17