Answer
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Work Step by Step
The end behaviors of a quadratic (or polynomial in general) function is determined by its leading coefficient $a$. When $a\gt 0$, the term $ax^2$ will go to $\infty$ when $x\to\infty$, which means that the curve will open up. When $a\lt 0$, the term $ax^2$ will go to $-\infty$ when $x\to\infty$, which means that the curve will open down.
