Chapter 4.4, Problem 2TU

TEST YOUR UNDERSTANDING | FOR EXAMPLE $4.11$

A small dog will weigh $20\text{pounds}$ at adulthood. The following table shows the weight $w$, in $\text{pounds}$, of the dog $t\text{months}$ after birth. The difference $D$ between the maximum weight of $20\text{pounds}$ and the current weight $W$, in $\text{pounds}$, is recorded in the third row of the table.

$t=time,inmonths$	$2$	$4$	$7$	$8$	$10$
$W=weight,inpounds$	$5.0$	$10.5$	$15.5$	$17.0$	$19.0$
$D=20-W$	$15.0$	$9.5$	$4.5$	$3.0$	$1.0$

Find an exponential model for $D$ as a function of $t$. Use your model for $D$ to give a formula for $W$ in terms of $t$.