18 choose 7
=C(18,7)
=18!/(7!(18-7)!)
=31824
OR
18 choices for first passenger,
17 choices for second passenger,
....
12 choices for 7th passenger,
so total = 18*17*16...12
but there are 7! ways to order the 7 passengers, so
number of groups
=18*17*16...12/7!
=31824 as well
A - bi would be the other complex zero.
When you take the sqrt when solving an equation you get a + and - solution.
The answer is 12.48 hope this helps!
13 is 141. A octagon has 1080 degrees and if you add all the angles up you get 939 and 1080-930=141
