Finding the Vertex of the Parabola $ h(x) = x^2 - 4x + c $: A Step-by-Step Solution

When analyzing quadratic functions, identifying the vertex is essential for understanding the graph’s shape and behavior. In this article, we explore how to find the vertex of the parabola defined by $ h(x) = x^2 - 4x + c $, using calculus and algebraic methods to confirm its location and connection to a specified point.


Understanding the Context

Understanding the Vertex of a Parabola

The vertex of a parabola given by $ h(x) = ax^2 + bx + c $ lies on its axis of symmetry. The x-coordinate of the vertex is found using the formula:

$$
x = rac{-b}{2a}
$$

For the function $ h(x) = x^2 - 4x + c $:

Key Insights

  • $ a = 1 $
  • $ b = -4 $

Applying the formula:

$$
x = rac{-(-4)}{2(1)} = rac{4}{2} = 2
$$

This confirms the vertex occurs at $ x = 2 $, consistent with the given condition.


Final Thoughts

Determining the y-Coordinate of the Vertex

To find the full vertex point $ (2, h(2)) $, substitute $ x = 2 $ into the function:

$$
h(2) = (2)^2 - 4(2) + c = 4 - 8 + c = -4 + c
$$

We are given that at $ x = 2 $, the function equals 3:
$$
h(2) = 3
$$

Set the expression equal to 3:

$$
-4 + c = 3
$$

Solving for $ c $:

$$
c = 3 + 4 = 7
$$


Summary of the Vertex and Function Behavior