text: ## Algebra and Trigonometry 10th Edition
  
  $t=-\frac{b}{2a}$
  This situation is represented by the vertex of the parabola: Vertex: $(-\frac{b}{2a},f(-\frac{b}{2a}))$ So, $t=-\frac{b}{2a}$ and $P(t)=f(-\frac{b}{2a}))$