令y=0
f(x) = f(x)+f(0)
∴f(0) = 0
令y = - x
f(x-x) = f(x)+f(-x) = f(0) = 0
f(-x) = - f(x)
∴f(x)是奇函数
令x=y=m/2
f(m) = 2f(m/2)
1/2 f(m) = f(m/2)
1/2 f(x²) - f(x) > 1/2 f(bx) - f(b)
f(x²/2) + f(-x) > f(bx/2) + f(-b)
f(x²/2 - x) > f(bx/2 - b)
x²/2 - x < bx/2 - b
x² - (2+b)x + 2b < 0
(x-2)(x-b) < 0
当 b=2时,解集为 空集
当b>2时,2 < x < b
当 b < 2时,b < x < 2