R,R\mathbb{R}, \mathbb{R}R,R
R,f(x)≤4\mathbb{R}, f(x) \leq 4R,f(x)≤4
x≥4,Rx \geq 4, \mathbb{R}x≥4,R
R,x≥3\mathbb{R}, x \geq 3R,x≥3