Math Problem Statement

A quadratic function y, equals, f, of, xy=f(x) is plotted on a graph and the vertex of the resulting parabola is left parenthesis, minus, 3, comma, minus, 6, right parenthesis(−3,−6). What is the vertex of the function defined as g, of, x, equals, minus, f, of, x, minus, 3g(x)=−f(x)−3?

Solution

The problem involves transforming a quadratic function and determining how the vertex changes.

Given:

  • The function f(x)f(x) is quadratic, and its vertex is at (3,6)(-3, -6).
  • The new function is defined as g(x)=f(x)3g(x) = -f(x) - 3.

Step-by-step solution:

  1. Original function: Since f(x)f(x) is quadratic and its vertex is (3,6)(-3, -6), we can assume the general form of the quadratic function is: f(x)=a(x+3)26f(x) = a(x + 3)^2 - 6 Here, aa is the leading coefficient of the quadratic function, and the vertex form of a quadratic is f(x)=a(xh)2+kf(x) = a(x - h)^2 + k, where (h,k)(h, k) is the vertex. In this case, h=3h = -3 and k=6k = -6.

  2. Transformation: Now, let's analyze the new function g(x)=f(x)3g(x) = -f(x) - 3.

    • First, we reflect f(x)f(x) across the x-axis by multiplying by -1: f(x)=[a(x+3)26]=a(x+3)2+6-f(x) = -[a(x + 3)^2 - 6] = -a(x + 3)^2 + 6
    • Then, we subtract 3 from this result: g(x)=a(x+3)2+63=a(x+3)2+3g(x) = -a(x + 3)^2 + 6 - 3 = -a(x + 3)^2 + 3
  3. New vertex: The new function g(x)=a(x+3)2+3g(x) = -a(x + 3)^2 + 3 is still in the vertex form, and the vertex of this function is at (3,3)(-3, 3).

    • The horizontal shift is the same as for f(x)f(x), so the x-coordinate of the vertex remains 3-3.
    • The vertical shift changes because of the transformations. The original function had a vertex at (3,6)(-3, -6). Reflecting it across the x-axis moved the vertex to (3,6)(-3, 6), and then subtracting 3 moved the vertex down to (3,3)(-3, 3).

Final Answer:

The vertex of g(x)=f(x)3g(x) = -f(x) - 3 is (3,3)\boxed{(-3, 3)}.

Would you like more details or have any questions about this transformation?

Here are 5 related questions to expand your understanding:

  1. How does changing the leading coefficient aa affect the vertex of a quadratic function?
  2. What is the effect of reflecting a quadratic function across the x-axis?
  3. How does adding or subtracting constants outside the function affect its graph?
  4. How can you find the vertex of a quadratic function given its standard form?
  5. What happens to the symmetry of the parabola when you reflect it?

Tip: The vertex form of a quadratic function is a powerful tool for quickly identifying key transformations like shifts and reflections.

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Vertex Transformation
Reflections
Vertical Shifts

Formulas

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

Theorems

Transformation of functions
Reflection of a quadratic function

Suitable Grade Level

Grades 9-12