Sangeetha Pulapaka
1

The equation for an exponential function is y = ab^{x} where a is the initial amount,, b is the common growth/decay factor and x is the time, the independent variable.

1. The output y = v (value in dollars, The initial amount is, a = 400,000, b = 2 (since the value is doubling each decade) and, x = d (time is in decades). The equation will be v = (400,000) \cdot 2^{d}.
2. When d = -1. v = 400,000 \cdot 2^{-1} = 200,000. This means that a year back, the value was $200,000. 3. Suppose d = -2, we plug in d = -2, in the equation to get v = 400,000 \cdot 2^{-2} = \frac{400000}{4} = 100,000, and we get the value as v =$100,000. This means that the value of the home in 2013 was \$100,000..d=−2 signifies the value of the home 2 years back in 2013