Answer
a. $D(0) = 3500$ $ D(15) = 6875$
b. 2025
c. 225
Work Step by Step
$D(t) = 3500 + 15t^2$
a. Find D(0) and D(15)
$D(0) = 3500 + 15(0)^2 = 3500$
$D(15) = 3500 + 15(15)^2 = 6875$
This represents the amount she deposited in $1995 (D(0))$ and $2010 (D(15))$
b. $17000 = 3500 + 15t^2$
$13500 = 15t^2$
$900 = t^2$
$t = 30$
In 1995 + 30 = 2025
c. Average Rate of Change (from t=0 to t=15): $\frac{D(15) - D(0)}{15-0} = \frac{3375}{15} = 225$
