Answer
it makes sense.
Work Step by Step
It makes sense.
When $a>0$, the parabola opens upward — like a smile.
When $a<0$, the parabola opens downward — like a frown.
So the given sentence sentence:
“Parabolas that open up appear to form smiles (a > 0), while parabolas that open down frown (a < 0)”
is both mathematically accurate and visually intuitive.
