In the following tasks, note the properties of binomial symbols.
For which natural numbers n are 
, 
, 
the first three terms of the geometric sequence?
We have a polynomial 
. For which natural number n (n> 1) are the coefficients 
and 
of this polynomial equal?
Three different parallel lines p, q and r and 12 different points are drawn in the plane:
5 points lie on a line p
4 points on the line q
3 points on the line r.
How many triangles with vertices at these points can we draw if one side of the triangle is to lie on the line p?
How many trapeziums with vertices at these points can we draw if one base of the trapezium is to lie on the line p?
or 
, 
.
