The substitution is
\The expression for velocity of falling object is
.
Differentiate on each side with respect to
..

.
Logistic differential equation is
.
Thus, 

Replace
in the expression. \ \

.
(b)
\Consider
.
Solution for the linear differential equation
is
.


.
From 9.4.7
.
Compare the both equations, here
.
(a)
.
(b)
.