A sand dune stands 5 feet above sea level. The hill is eroding at a rate of 1 foot per 20 years. Let y represent the height of the sand dune after x years. Which equation represents the situation?
The given 5 feet above sea level could be taken as the y-intercept, while the rate of -1 foot per 20 years could be taken as the slope. The height y is a function of time. Using y-intercept slope form of a line:
Y = (-1/20)t + 5
