Question

In what direction does the graph of `y = x^2 -8x + 16` open?

Answer 1

Look at the sign of `a`.
`+a rarr` opens upwards and `-a rarr` opens downwards

Explanation:

If you have the equation of a parabola you can always tell which way it is open by looking at the sign of the `x^2` term.

If `a > 0` (ie positive,) then there is a minimum turning point, the parabola is the 'right way up' and opens upwards.

If `x <0` (ie negative,) then there is a maximum turning point, parabola is "upside down and opens downwards.