Math Problem Statement

Determine the equation of the quadratic function g shown in the figure and the points where its graph intercepts the coordinate axes.

Solution

The problem asks to determine the equation of the quadratic function gg, as well as the intercepts with the axes, based on the provided graph.

Step 1: Identify key points from the graph

From the image:

  • The graph of the function is a parabola that opens upwards.
  • The vertex of the parabola appears to be at approximately (1,2)(1, -2), suggesting this is a minimum point.
  • The parabola intersects the y-axis at a point approximately y=2y = -2.
  • Another important point given on the graph is around (4,5)(4, 5).

Step 2: General form of a quadratic function

The general form of a quadratic function is: g(x)=a(xh)2+kg(x) = a(x - h)^2 + k where (h,k)(h, k) is the vertex of the parabola. From the graph, the vertex appears to be at (1,2)(1, -2), so we substitute h=1h = 1 and k=2k = -2 to get: g(x)=a(x1)22g(x) = a(x - 1)^2 - 2

Step 3: Use another point to find aa

We can now substitute another known point to solve for the value of aa. From the graph, the point (4,5)(4, 5) lies on the curve. Substituting x=4x = 4 and y=5y = 5 into the equation: 5=a(41)225 = a(4 - 1)^2 - 2 5=a(3)225 = a(3)^2 - 2 5=9a25 = 9a - 2 7=9a7 = 9a a=79a = \frac{7}{9}

Step 4: Write the equation of the function

Thus, the equation of the quadratic function is: g(x)=79(x1)22g(x) = \frac{7}{9}(x - 1)^2 - 2

Step 5: Find the intercepts

  • Y-intercept: Set x=0x = 0 in the equation: g(0)=79(01)22=792=1.22g(0) = \frac{7}{9}(0 - 1)^2 - 2 = \frac{7}{9} - 2 = -1.22 Thus, the y-intercept is approximately (0,1.22)(0, -1.22).

  • X-intercepts: Set g(x)=0g(x) = 0 and solve for xx: 0=79(x1)220 = \frac{7}{9}(x - 1)^2 - 2 79(x1)2=2\frac{7}{9}(x - 1)^2 = 2 (x1)2=187(x - 1)^2 = \frac{18}{7} x1=±187±1.6x - 1 = \pm \sqrt{\frac{18}{7}} \approx \pm 1.6 x=1±1.6x = 1 \pm 1.6 So, the x-intercepts are approximately x=2.6x = 2.6 and x=0.6x = -0.6.

Final Results:

  • The quadratic equation is g(x)=79(x1)22g(x) = \frac{7}{9}(x - 1)^2 - 2.
  • Y-intercept: (0,1.22)(0, -1.22).
  • X-intercepts: approximately (0.6,0)(-0.6, 0) and (2.6,0)(2.6, 0).

Do you have any questions or would you like further details?


Related Questions:

  1. What is the significance of the vertex in the graph of a quadratic function?
  2. How can we use symmetry to predict the intercepts of a quadratic function?
  3. Can you calculate the roots of the quadratic equation using the quadratic formula?
  4. How does the value of aa in the equation affect the shape of the parabola?
  5. What is the relationship between the axis of symmetry and the vertex of a quadratic function?

Tip:

When finding intercepts of quadratic functions, setting y=0y = 0 gives the x-intercepts, while setting x=0x = 0 gives the y-intercept.

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Parabolas
Intercepts

Formulas

g(x) = a(x - h)^2 + k
X-intercepts: solve g(x) = 0
Y-intercept: set x = 0 in g(x)

Theorems

Properties of Quadratic Functions
Vertex Form of a Parabola

Suitable Grade Level

Grades 9-11