Math Problem Statement

  1. In the figure, the vertex of the graph of a quadratic function y = f(x) is (–2 , 5) and the y-intercept is –3. Find f(x).

Solution

To find the quadratic function f(x)f(x) given its vertex and y-intercept, we'll use the vertex form of a quadratic function and some additional information.

The vertex form of a quadratic function is: f(x)=a(xh)2+kf(x) = a(x - h)^2 + k where (h,k)(h, k) is the vertex of the parabola.

Given:

  • Vertex: (2,5)(-2, 5)
  • Y-intercept: (0,3)(0, -3)

First, plug in the vertex into the vertex form: f(x)=a(x+2)2+5f(x) = a(x + 2)^2 + 5

Next, use the y-intercept to find the value of aa. The y-intercept means when x=0x = 0, f(x)=3f(x) = -3. Plug these values into the function: 3=a(0+2)2+5-3 = a(0 + 2)^2 + 5 3=a(4)+5-3 = a(4) + 5 3=4a+5-3 = 4a + 5 35=4a-3 - 5 = 4a 8=4a-8 = 4a a=2a = -2

So the quadratic function is: f(x)=2(x+2)2+5f(x) = -2(x + 2)^2 + 5

Let's expand this to confirm it fits the given conditions: f(x)=2(x2+4x+4)+5f(x) = -2(x^2 + 4x + 4) + 5 f(x)=2x28x8+5f(x) = -2x^2 - 8x - 8 + 5 f(x)=2x28x3f(x) = -2x^2 - 8x - 3

Thus, the quadratic function is: f(x)=2x28x3f(x) = -2x^2 - 8x - 3

Would you like more details or have any questions? Here are some additional questions you might find interesting:

  1. How do you find the vertex of a quadratic function given its standard form?
  2. What are the steps to convert a quadratic function from standard form to vertex form?
  3. How do you determine the axis of symmetry of a quadratic function?
  4. What is the significance of the discriminant in a quadratic equation?
  5. Can you derive the quadratic formula from the general form of a quadratic equation?

Tip: To quickly determine the vertex form from the standard form ax2+bx+cax^2 + bx + c, use the formula for the vertex: h=b2ah = -\frac{b}{2a} and k=f(h)k = f(h).

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Vertex Form
Y-intercept

Formulas

Vertex form of a quadratic function: f(x) = a(x - h)^2 + k

Theorems

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Suitable Grade Level

Grades 9-12