The increasing function y = f (x) defined on R has f (x + y) = f (x) + F (y) for any x, y belonging to R Find f (0) To prove that f (x) is an odd function Solving inequality f (3x) + F (x + 1) < 0

The increasing function y = f (x) defined on R has f (x + y) = f (x) + F (y) for any x, y belonging to R Find f (0) To prove that f (x) is an odd function Solving inequality f (3x) + F (x + 1) < 0

one
Let y = 0
f(x)=f(x)+f(0)
f(0)=0
two
Let y = - X
f(x)+f(-x)=f(0)=0
F (x) is an odd function
three
f(3x)+f(x+1)