For each equation below identify what type of equation it is (linear or exponential), which variable is the independent variable (name it) and which variable (name it) is dependent in the following problem, then identify the parameters (linear: slope and y-intercept; or exponential: initial value and growth rate) and explain the meaning of each of these parameters in the context of each problem:
a) A recent study found that years of schooling (hint: 12 = graduated high school) predicted average weekly earnings (in dollars) via the equation y = -645.25+108.25x.
b) The average yearly cost of college tuition (dollars) has increased by a constant factor each year since the year 1990 via the equation: f(t) = 8421(1.02)t.