Math Problem Statement

Solve the following system of equations by graphing: 1. y = -x^2 + 2x + 7 2. y = 2x + 7

Solution

To solve the system of equations by graphing:

The system is:

  1. y=x2+2x+7y = -x^2 + 2x + 7 (a quadratic equation, representing a parabola).
  2. y=2x+7y = 2x + 7 (a linear equation, representing a straight line).

Steps:

  1. Graph the quadratic equation:

    • y=x2+2x+7y = -x^2 + 2x + 7.
    • This is a parabola that opens downward (due to the negative coefficient of x2x^2).
    • Find the vertex:
      • The x-coordinate of the vertex is x=b2a=22(1)=1x = -\frac{b}{2a} = -\frac{2}{2(-1)} = 1.
      • Substitute x=1x = 1 into the equation to find yy: y=(1)2+2(1)+7=8y = -(1)^2 + 2(1) + 7 = 8.
      • Vertex: (1,8)(1, 8).
    • Additional points:
      • Substitute x=0x = 0: y=7y = 7 (point (0,7)(0, 7)).
      • Substitute x=2x = 2: y=4+4+7=7y = -4 + 4 + 7 = 7 (point (2,7)(2, 7)).
  2. Graph the linear equation:

    • y=2x+7y = 2x + 7.
    • This is a straight line with slope 2 and y-intercept 7.
    • Points to graph:
      • When x=0x = 0: y=7y = 7 (point (0,7)(0, 7)).
      • When x=1x = -1: y=5y = 5 (point (1,5)(-1, 5)).
      • When x=1x = 1: y=9y = 9 (point (1,9)(1, 9)).
  3. Find points of intersection:

    • Solve x2+2x+7=2x+7-x^2 + 2x + 7 = 2x + 7 algebraically:
      • x2+2x+72x7=0-x^2 + 2x + 7 - 2x - 7 = 0,
      • x2=0-x^2 = 0,
      • x=0x = 0.
    • Substitute x=0x = 0 into y=2x+7y = 2x + 7: y=7y = 7.
      • Point of intersection: (0,7)(0, 7).

Final Answer:

The parabola and line intersect at one point: (0,7)(0, 7).

If you have further questions or want a graph of the solution, let me know!

Here are related questions for deeper understanding:

  1. How do you determine the vertex of a parabola from its equation?
  2. Why does the parabola open downward in this case?
  3. How can you algebraically confirm the number of intersections in a quadratic-linear system?
  4. What is the significance of the slope in the linear equation?
  5. How does the discriminant help in identifying the number of solutions?

Tip: Always check for symmetry when graphing a parabola for quicker plotting.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Systems
Graphing Equations

Formulas

Quadratic equation in standard form: y = ax^2 + bx + c
Linear equation in slope-intercept form: y = mx + b
Vertex formula for a parabola: x = -b / (2a)

Theorems

Properties of parabolas (vertex, symmetry, direction)
Intersection of curves

Suitable Grade Level

Grades 8-10