Math Problem Statement

Fitting Exponential Functions to Data. Graph the given data on a coordinate plane, determine whether the data exhibits linear or exponential behavior, and write an equation for the data.

Solution

Let's analyze the problem step by step.

Provided Information:

  • Time (years): 0, 1, 2, 3, 4, 5
  • Depreciation (dollars): 990, 500, 250, 110, 60, 25

Problem Breakdown:

  1. Graph the Data: We will plot the data points (Time, Depreciation) on a coordinate plane:

    • Points: (0, 990), (1, 500), (2, 250), (3, 110), (4, 60), (5, 25)
  2. Determine Behavior (Linear or Exponential): Compare the rate of change. Exponential behavior typically involves a consistent ratio between successive terms, while linear behavior involves a consistent difference.

  3. Write an Equation: We will fit the data using an exponential decay function:
    y=abxy = a \cdot b^x
    where:

    • aa is the initial value at x=0x = 0,
    • bb is the base (decay factor).

Let me perform the calculations and sketch the graph. numpy as np import matplotlib.pyplot as plt

Data points

time = np.array([0, 1, 2, 3, 4, 5]) depreciation = np.array([990, 500, 250, 110, 60, 25])

Plotting the graph

plt.figure(figsize=(8, 5)) plt.scatter(time, depreciation, color='blue', label='Data Points') plt.plot(time, depreciation, linestyle='--', color='red', label='Trend Line') plt.title("Depreciation of Computer Value Over Time") plt.xlabel("Time (Years)") plt.ylabel("Depreciation (Dollars)") plt.grid(True) plt.legend() plt.show()### Step 1: Graph of the Data The scatter plot shows the depreciation data over time. The trend line (dashed red) illustrates the decreasing value of the computer.

Step 2: Behavior Analysis

This data exhibits exponential decay rather than linear behavior because the depreciation does not decrease by a constant amount (as seen in linear behavior). Instead:

  • The ratio of successive values is approximately constant. For example: 5009900.505,250500=0.5,1102500.44,601100.545\frac{500}{990} \approx 0.505, \quad \frac{250}{500} = 0.5, \quad \frac{110}{250} \approx 0.44, \quad \frac{60}{110} \approx 0.545

Step 3: Finding the Exponential Decay Equation

The general equation is: y=abxy = a \cdot b^x

  • At x=0x = 0, y=a=990y = a = 990.
  • To find bb, calculate the ratio between consecutive values:
    b5009900.505b \approx \frac{500}{990} \approx 0.505

The equation becomes: y=990(0.505)xy = 990 \cdot (0.505)^x

Would you like further details, such as step-by-step verification or a refined graph of the equation? Here are some follow-up questions to explore further:

  1. Would you like me to verify the exponential equation against all data points?
  2. Should I calculate the percentage error of this model?
  3. Do you need a detailed explanation of why the data is not linear?
  4. Would you like me to extend the graph for predictions beyond 5 years?
  5. Should I create a step-by-step guide for finding the equation manually?

Tip: In exponential decay, values decrease rapidly at first and then level off, forming an asymptote.

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Math Problem Analysis

Mathematical Concepts

Exponential Functions
Graphing
Data Analysis

Formulas

Exponential decay function: y = a * b^x
Ratio test for exponential behavior: b = successive_value / previous_value

Theorems

Exponential Decay Theory

Suitable Grade Level

Grades 9-12