Math Problem Statement

Which function, f(x) = x(x - 6) or g(x) = (x + 3)^2 - 8, has the lower minimum?

Solution

To determine which function, f(x)=x(x6)f(x) = x(x - 6) or g(x)=(x+3)28g(x) = (x + 3)^2 - 8, has the lower minimum, let us analyze each function.


1. Analyze f(x)=x(x6)f(x) = x(x - 6):

Simplify: f(x)=x26xf(x) = x^2 - 6x

This is a quadratic function in standard form: f(x)=ax2+bx+cf(x) = ax^2 + bx + c Here, a=1a = 1, b=6b = -6, and c=0c = 0. Since a>0a > 0, the parabola opens upwards, and the vertex represents the minimum value.

The xx-coordinate of the vertex is given by: x=b2a=62(1)=3x = -\frac{b}{2a} = -\frac{-6}{2(1)} = 3

Substitute x=3x = 3 back into f(x)f(x) to find the minimum value: f(3)=3(36)=3(3)=9f(3) = 3(3 - 6) = 3(-3) = -9

Thus, the minimum value of f(x)f(x) is: Minimum of f(x)=9\text{Minimum of } f(x) = -9


2. Analyze g(x)=(x+3)28g(x) = (x + 3)^2 - 8:

This is already in vertex form: g(x)=(x+3)28g(x) = (x + 3)^2 - 8

The vertex occurs at x=3x = -3, and the value of g(x)g(x) at the vertex is: g(3)=((3)+3)28=08=8g(-3) = ((-3) + 3)^2 - 8 = 0 - 8 = -8

Thus, the minimum value of g(x)g(x) is: Minimum of g(x)=8\text{Minimum of } g(x) = -8


Comparison of Minimum Values:

  • Minimum of f(x)f(x): 9-9
  • Minimum of g(x)g(x): 8-8

Since 9<8-9 < -8, f(x)f(x) has the lower minimum.


Let me know if you want a deeper explanation or any additional details!

Here are 5 related questions you might consider:

  1. How do we determine the vertex of a quadratic function?
  2. Can the minimum of a quadratic function change if the equation is shifted horizontally?
  3. What is the significance of the parabola's direction (upward vs downward)?
  4. How can we graphically compare the two functions f(x)f(x) and g(x)g(x)?
  5. What are the general steps to convert a quadratic function to vertex form?

Tip: Always identify the direction of a parabola (upward or downward) before calculating its minimum or maximum!

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Math Problem Analysis

Mathematical Concepts

Quadratic Functions
Vertex Form
Parabolas
Minimum Values

Formulas

Vertex formula: x = -b/(2a)
Standard quadratic form: ax² + bx + c

Theorems

Properties of Parabolas (direction of opening, vertex as minimum)

Suitable Grade Level

High School (Grades 9-12)