| Quadratic function | Graph | Roots |
|---|---|---|
\(y = a(x - h)^2 - k \) | \( h\pm\sqrt{\frac{k}{a}}\) | |
\(y = -a(x - h)^2 + k \) | \( h\pm\sqrt{\frac{k}{a}}\) |
Take \(a\ne0\). The displayed roots are real when \(k/a\ge0\); they coincide when \(k=0\). In the illustrated upward/downward cases, \(a>0\).
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