Math Problem Statement

The table gives selected values for a function f.

x 2 3 4 5 f (x) 4 9 18 31

Which of the following statements is consistent with the table of values? The expression for the average rate of change is 4a – 4, and f is quadratic. The expression for the average rate of change is 4a – 4, and f is linear. The expression for the average rate of change is 5a – 6, and f is quadratic. The expression for the average rate of change is 5a – 6, and f is linear.

Solution

To determine which statement is consistent with the table of values, we will first calculate the average rate of change of the function f(x)f(x) between different points and then try to match it with the provided expressions.

The values provided in the table are:

x=2,3,4,5andf(x)=4,9,18,31x = 2, 3, 4, 5 \quad \text{and} \quad f(x) = 4, 9, 18, 31

Step 1: Calculate the average rate of change.

The average rate of change between two points x1x_1 and x2x_2 for a function f(x)f(x) is given by:

Average Rate of Change=f(x2)f(x1)x2x1\text{Average Rate of Change} = \frac{f(x_2) - f(x_1)}{x_2 - x_1}

Let’s compute the average rate of change between consecutive values:

  1. Between x=2x = 2 and x=3x = 3:

f(3)f(2)32=9432=51=5\frac{f(3) - f(2)}{3 - 2} = \frac{9 - 4}{3 - 2} = \frac{5}{1} = 5

  1. Between x=3x = 3 and x=4x = 4:

f(4)f(3)43=18943=91=9\frac{f(4) - f(3)}{4 - 3} = \frac{18 - 9}{4 - 3} = \frac{9}{1} = 9

  1. Between x=4x = 4 and x=5x = 5:

f(5)f(4)54=311854=131=13\frac{f(5) - f(4)}{5 - 4} = \frac{31 - 18}{5 - 4} = \frac{13}{1} = 13

Step 2: Check if the function is quadratic or linear.

  • A linear function has a constant rate of change. Since the rate of change (5, 9, 13) is not constant, the function cannot be linear.

  • A quadratic function has a second difference that is constant. Let's check the second differences of the average rate of change:

First differences of the rates of change: 95=4,139=49 - 5 = 4, \quad 13 - 9 = 4 The second difference is constant (4), which is a characteristic of a quadratic function.

Thus, f(x)f(x) is quadratic.

Step 3: Compare the given expressions.

Now let's check the given options:

  • The expression for the average rate of change is 4a44a - 4 and ff is quadratic.
  • The expression for the average rate of change is 5a65a - 6 and ff is quadratic.

Since we know the function is quadratic, we can eliminate options that say ff is linear. This leaves us with two options to compare the expressions 4a44a - 4 and 5a65a - 6 to our calculations of average rates of change.

None of the options perfectly match our calculated rates of change, but based on the second difference and quadratic nature, the correct answer would be:

The expression for the average rate of change is 5a65a - 6, and ff is quadratic.

Would you like more details on any step or further clarifications?

Here are 5 related questions:

  1. How do you calculate the second difference for quadratic functions?
  2. What are some examples of quadratic functions in real life?
  3. How does the average rate of change differ between linear and quadratic functions?
  4. How can you derive a quadratic function given points on a table?
  5. What is the significance of the second difference being constant?

Tip: For quadratic functions, the second difference of consecutive outputs is always constant.

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Math Problem Analysis

Mathematical Concepts

Average Rate of Change
Quadratic Functions

Formulas

Average Rate of Change formula: (f(x2) - f(x1)) / (x2 - x1)
Quadratic function second difference: constant second difference

Theorems

Properties of Quadratic Functions

Suitable Grade Level

Grades 9-12