Question 1

What if the discriminant is negative?

Accepted Answer

The equation has no real roots; the parabola stays entirely above or below the x-axis. The roots are complex conjugates p ± qi.

Question 2

Can I factor instead of using the formula?

Accepted Answer

Yes, when the roots are rational. Look for two numbers whose product is ac and sum is b. The formula always works.

Question 3

How do I find the axis of symmetry?

Accepted Answer

It is the vertical line x = −b/(2a), which passes through the vertex and lies halfway between the roots.

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