The function f(x) describes a parabola that opens downward. The only graph with that shape is the 2nd one.
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The degree of 2 on the x² term means there will be only 1 turning point (1 less than the degree). The bottom two choices have more turning points than that.
The minus sign on the coefficient of x² means the graph opens downward—that it tends toward -∞ when x gets very large in magnitude, either positive or negative.
