1. **State the problem:** We have membership data for years 2000, 2005, 2010, and 2015 with values 11,100,000; 12,600,000; 14,100,000; and 15,600,000 respectively. We want to analyze the trend and find the linear function that models this data. 2. **Formula used:** For a linear function $y = mx + b$, where $m$ is the slope and $b$ is the y-intercept. 3. **Calculate the slope $m$:** The slope is the change in membership divided by the change in years. $$m = \frac{15,600,000 - 11,100,000}{2015 - 2000} = \frac{4,500,000}{15} = 300,000$$ 4. **Find the y-intercept $b$:** Use one data point, for example year 2000 with membership 11,100,000. $$11,100,000 = 300,000 \times 2000 + b$$ $$b = 11,100,000 - 300,000 \times 2000 = 11,100,000 - 600,000,000 = -588,900,000$$ 5. **Write the linear equation:** $$y = 300,000x - 588,900,000$$ 6. **Interpretation:** This equation models the membership growth as a linear increase of 300,000 members per year starting from the year 2000. 7. **Summary:** The membership increases steadily by 300,000 every year, forming a straight line on the graph as described.