Math Problem Statement

Graph the equation y = -x^2 + 6x - 5 on the accompanying set of axes. You must plot 5 points including the roots and the vertex. Using the graph, determine the roots of the equation -x^2 + 6x - 5 = 0.

Solution

To solve this problem, let's break down the task step-by-step.

Step 1: Analyze the Equation

The given equation is: y=x2+6x5y = -x^2 + 6x - 5 This equation represents a parabola that opens downward (since the coefficient of x2x^2 is negative).

Step 2: Find the Roots

To find the roots (x-intercepts) of the equation, we set y=0y = 0: x2+6x5=0-x^2 + 6x - 5 = 0 This can be rewritten as: x26x+5=0x^2 - 6x + 5 = 0 We solve this quadratic equation using the quadratic formula: x=(6)±(6)241521x = \frac{-(-6) \pm \sqrt{(-6)^2 - 4 \cdot 1 \cdot 5}}{2 \cdot 1} Simplifying, we get: x=6±36202x = \frac{6 \pm \sqrt{36 - 20}}{2} x=6±162x = \frac{6 \pm \sqrt{16}}{2} x=6±42x = \frac{6 \pm 4}{2} Thus, the roots are: x=6+42=5andx=642=1x = \frac{6 + 4}{2} = 5 \quad \text{and} \quad x = \frac{6 - 4}{2} = 1 So, the roots are x=5x = 5 and x=1x = 1.

Step 3: Find the Vertex

The vertex of a parabola in the form y=ax2+bx+cy = ax^2 + bx + c can be found using the formula: x=b2ax = -\frac{b}{2a} Here, a=1a = -1 and b=6b = 6, so: x=621=3x = -\frac{6}{2 \cdot -1} = 3 To find the y-coordinate of the vertex, substitute x=3x = 3 back into the equation: y=(3)2+635y = -(3)^2 + 6 \cdot 3 - 5 y=9+185y = -9 + 18 - 5 y=4y = 4 So, the vertex is at (3,4)(3, 4).

Step 4: Plot the Points

You need to plot five points, including the roots and the vertex. The key points are:

  1. Root at (1,0)(1, 0)
  2. Root at (5,0)(5, 0)
  3. Vertex at (3,4)(3, 4)

Step 5: Choose Two Additional Points

Let's select additional points to provide a more complete graph. For example:

  • When x=0x = 0: y=(0)2+605=5y = -(0)^2 + 6 \cdot 0 - 5 = -5 So, (0,5)(0, -5) is one point.

  • When x=6x = 6: y=(6)2+665y = -(6)^2 + 6 \cdot 6 - 5 y=36+365=5y = -36 + 36 - 5 = -5 So, (6,5)(6, -5) is another point.

Summary of Points to Plot

The points you should plot on the graph are:

  1. (1,0)(1, 0)
  2. (5,0)(5, 0)
  3. (3,4)(3, 4) (vertex)
  4. (0,5)(0, -5)
  5. (6,5)(6, -5)

These points will outline the parabola for y=x2+6x5y = -x^2 + 6x - 5.

Would you like further clarification on any of these steps or details on how to complete the graph?


Here are 5 related questions for further exploration:

  1. How do you determine if a parabola opens upwards or downwards?
  2. What does the vertex represent in a parabolic graph?
  3. How can you find the axis of symmetry for a parabola?
  4. How do you use the quadratic formula to find the roots of any quadratic equation?
  5. How would the graph change if the equation were y=x26x+5y = x^2 - 6x + 5 instead?

Tip: When graphing parabolas, always identify the vertex and the direction of opening first—it helps in sketching the graph accurately.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Functions
Graphing Parabolas

Formulas

Quadratic formula: x = (-b ± √(b^2 - 4ac)) / 2a
Vertex formula: x = -b / 2a

Theorems

Quadratic formula

Suitable Grade Level

Grades 8-10