it curves downward.
Step 4: Test End Behavior
Look at what the general shape of the graph will be, based on the values of y for very large values of ±x.
Using this analysis, we can always come up with a sketch of a curve.
And now, the rules.
(1)When f′(x) > 0, the curve is rising; when f′(x) < 0, the curve is falling; when f′(x) = 0, the
curve is at a critical point.(2)When f ́ ́(x) > 0, the curve is “concave up”; when f ́ ́(x) < 0, the curve is “concave down”;
and when f ́ ́(x) = 0, the curve is at a point of inflection.