Recall the binomial theorem.

1. The binomial expansion of
is

Observe that


When we multiply these by
,
•
and
combine to make 
•
and
combine to make 
and the sum of these terms is

2. The binomial expansion is

We get the
term when
:

30=1/2 inch
60=1/2x2=1 inch
90=1/2x3=1 1/2
shortest side is 1/2 inch, medium side is 1 inch, longest is 1 1/2
Answer:
2.2 hr
Step-by-step explanation:
Let t = time
95t = distance of westbound train
105t = distance of eastbound train
95t + 105t = 440
200t = 440
t = 2.2 hr.