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Is #y=x^2 + 3x - 15# a function?

Answer 1

Kennedy Adams

Yes, it is (in the usual sense that #y# is a function of #x#).

For any value of #x#, the expression gives only one (never two or more) values for #y#.

Here is the graph on #y=x^2+3x-15#. As you can see, it passes the vertical line test.

graph{y=x^2+3x-15 [-33.55, 31.4, -23.03, 9.46]}

(There are many times that 2 values of #x# give the same value of #y#, but that is ok for a function.)

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Answer 2

Jameson Allen

Yes, the quadratic equation (y = x^2 + 3x - 15) is a function.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.