We can write the equation of a parabola in two different ways:
The standard form:
[tex]\begin{gathered} y=ax^2+bx+c \\ a\ne0 \end{gathered}[/tex]And the vertex form:
[tex]y=a(x-h)^2+k[/tex]If the parabola has a minimum or a maximum depends on the leading coefficient (the coefficient of x²) or in both cases the coefficient a.
Let's see the cases:
[tex]a>0_{\text{ }}(a_{\text{ }}is_{\text{ }}positive)[/tex]If a is positive, the parabola opens upwards, so the parabola has a minimum.
[tex]a<0_{\text{ }}(a_{\text{ }}is_{\text{ }}negative)[/tex]If a is negative, the parabola opens downwards, so the parabola has a maximum
