Math Problem Statement

determine the domain and range of each function in interval notation and explain how you got the answer: a) f(x)=-3x+8 b) f(x)=-0.5(x+3)^2+4

Solution

Let's analyze both functions to determine their domains and ranges.


a) f(x)=3x+8f(x) = -3x + 8

Domain:

The function f(x)=3x+8f(x) = -3x + 8 is a linear function (a straight line). For any linear function, the domain is all real numbers because there are no restrictions on xx.

  • Domain: (,)(-\infty, \infty)

Range:

Since the function is linear, it will keep increasing or decreasing indefinitely. For this specific function, the slope is negative (3-3), meaning it decreases as xx increases. The output of the function can take any real value.

  • Range: (,)(-\infty, \infty)

b) f(x)=0.5(x+3)2+4f(x) = -0.5(x + 3)^2 + 4

Domain:

The function f(x)=0.5(x+3)2+4f(x) = -0.5(x + 3)^2 + 4 is a quadratic function (a parabola). Quadratic functions are defined for all real numbers because there is no restriction on xx.

  • Domain: (,)(-\infty, \infty)

Range:

The function is in the form of a parabola, and since the coefficient of (x+3)2(x + 3)^2 is negative (0.5-0.5), it opens downward. The vertex will give us the maximum value of the function.

  • The vertex occurs at x=3x = -3, as that makes the square term zero.

  • Substituting x=3x = -3 into the function:

    f(3)=0.5(3+3)2+4=0.5(0)+4=4f(-3) = -0.5(-3 + 3)^2 + 4 = -0.5(0) + 4 = 4

Since the parabola opens downward, the maximum value of f(x)f(x) is 4. As xx moves away from 3-3, the value of f(x)f(x) decreases indefinitely.

  • Range: (,4](-\infty, 4]

Summary:

a) For f(x)=3x+8f(x) = -3x + 8:

  • Domain: (,)(-\infty, \infty)
  • Range: (,)(-\infty, \infty)

b) For f(x)=0.5(x+3)2+4f(x) = -0.5(x + 3)^2 + 4:

  • Domain: (,)(-\infty, \infty)
  • Range: (,4](-\infty, 4]

Would you like any further explanation or details on these functions? Here are a few related questions for deeper understanding:

  1. How does the slope of a linear function affect its range?
  2. What is the significance of the vertex in a quadratic function?
  3. How do you determine the range of a quadratic function from its equation?
  4. How does the direction in which a parabola opens affect the range?
  5. How can you find the domain and range of rational functions?

Tip: For quadratic functions, the vertex gives key information about the maximum or minimum value of the function, depending on whether the parabola opens upward or downward.

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Math Problem Analysis

Mathematical Concepts

Functions
Domain and Range
Linear Functions
Quadratic Functions
Interval Notation

Formulas

f(x) = mx + b (for linear functions)
f(x) = a(x - h)^2 + k (for quadratic functions)

Theorems

Domain of linear functions: All real numbers
Domain of quadratic functions: All real numbers
Range of a linear function: All real numbers
Range of a quadratic function: Dependent on vertex and direction of opening

Suitable Grade Level

Grades 8-10