Guess limits of a simple functions as x → +∞. lim_{x → +∞} 2x = +∞; x: 1, 2, 3, 4 → +∞; 2x: 2, 4, 6, 8 → +∞. lim_{x → +∞} (-2x) = -∞; x: 1, 2, 3, 4 → +∞; -2x: -2, -4, -6, -8 → -∞. lim_{x → +∞} 1/2x = 0; x: 1, 2, 3, 4 → +∞; 1/2x: 1/2, 1/4, 1/6, 1/8 → 0. lim_{x → +∞} -5/x^2 = 0; x: 1, 2, 3, 4 → +∞; -5/x^2: -5/12, -5/4, -5/9, -5/16 → 0.