If f (x) satisfies 2F (x) + F (- x) = 5x + 4, find f (x) and f (- x)

If f (x) satisfies 2F (x) + F (- x) = 5x + 4, find f (x) and f (- x)

2f(x)+f(-x)=5x+4 (1)
Let x = - X
2f(-x)+f(x)=-5x+4 (2)
(2)×2-(1)
3f(-x)=-10x+8-5x-4=-15x+4
So f (- x) = (4-15x) / 3