over the [tex]x[/tex]-axis, it could mean two things. it could mean on the [tex]x[/tex]-axis or it could mean above the [tex]x[/tex]-axis

if it means on the [tex]x[/tex]

-axisthen [tex]B[/tex] and [tex]D[/tex] are correct

if it means above the [tex]x[/tex]

-axis[tex]B[/tex] is correct

the value of [tex]c[/tex] is the value of [tex]y[/tex] when [tex]x = 0[/tex] (the point when the function crosses the y-axis)

since [tex]a > 0[/tex] and the function above x-axis, it must cross the positive y-axis (c is positive)

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when [tex]a > 0[/tex] and the turning point on the [tex]x[/tex] axis or above it

[tex]c[/tex] is positive

when [tex]a > 0[/tex] and the turning point below the [tex]x[/tex] axis

[tex]c[/tex] could be positive or negative

when [tex]a < 0[/tex] and the turning point on the [tex]x[/tex] axis or below it

[tex]c[/tex] is negative

when [tex]a < 0[/tex] and the turning point obove the [tex]x[/tex] axis

[tex]c[/tex] could be positive or negative

-Jambo