Which of the following accurately describes what the graph of y = 5x^2 + 50x + 125 looks like, with the repeated root of x = -5?

Statement #1: The graph opens downward.
Statement #2: The graph has a vertex to the right of the x-axis.
Statement #3: The graph touches the x-axis once.

Select the correct statement: Statement # \(\square\)

1 answer

To analyze the graph of the quadratic function \(y = 5x^2 + 50x + 125\) with the repeated root at \(x = -5\), we can evaluate each of the statements given.

  1. Determining if the graph opens downward: The leading coefficient of \(x^2\) in the equation \(y = 5x^2 + 50x + 125\) is \(5\), which is positive. This means that the graph opens upward.

    • Statement #1: The graph opens downward. (False)
  2. Finding the vertex: The vertex of a parabola in the form \(y = ax^2 + bx + c\) can be found using the vertex formula \(x = -\frac{b}{2a}\). Here, \(a = 5\) and \(b = 50\). \[ x = -\frac{50}{2 \cdot 5} = -\frac{50}{10} = -5 \] The vertex is at \(x = -5\), which is to the left of the x-axis (i.e., less than \(0\)).

    • Statement #2: The graph has a vertex to the right of the x-axis. (False)
  3. Understanding the x-axis intersections: A quadratic function with a repeated root means it touches the x-axis at a single point. Since \(x = -5\) is the repeated root, the graph will indeed touch the x-axis at this point.

    • Statement #3: The graph touches the x-axis once. (True)

Based on this analysis, the correct statement is:

Statement #3: The graph touches the x-axis once.

So the correct answer is Statement # \(3\).