Problems

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We consider a function y=f(x) defined on the whole set of real numbers and satisfying f(x+k)×(1f(x))=1+f(x) for some number k0. Prove that f(x) is a periodic function.

The function f(x) for each real value of x(,+) satisfies the equality f(x)+(x+1/2)×f(1x)=1.

a) Find f(0) and f(1). b) Find all such functions f(x).

The function F is given on the whole real axis, and for each x the equality holds: F(x+1)F(x)+F(x+1)+1=0.

Prove that the function F can not be continuous.

Let z1 and z2 be fixed points of a complex plane. Give a geometric description of the sets of all points z that satisfy the conditions:

a) argzz1zz2=0;

b) argz1zzz2=0.