Final answer:
Both investment plans have increasing functions. Plan II has a greater unit rate of $420 per month versus Plan I's $400 per month. Plan I has a greater initial investment with a y-intercept of $12,000, compared to Plan II's $11,000.
Step-by-step explanation:
To compare the two investment plans for William, we need to understand the structure of each plan and recognize that the function for each plan represents how the total investment grows over time. Plan I requires an initial investment of $12,000 with an additional $400 invested every month.
Plan II is represented by the function y = 11,000 + 420x, where y is the total amount invested and x is the number of months.
The functions for both plans are increasing, as additional money is added over time.
The function for plan II has a greater unit rate of $420 per month, compared to Plan I's $400 per month.
The function for plan I has a greater y-intercept at $12,000, as opposed to Plan II's y-intercept at $11,000. This means Plan I starts with a higher initial investment.