f(x) = 2x + sinx ⇒ f'(x) = 2 + cosx ≥ 1 > 0 [∵ -1 ≤ cos x ≤ 1] ∴ 1 ≤ 2 + cos x ≤ 3 ⇒ f is strictly increasing on ⇒ f is one - one on Again as every vertical line does not meet the graph of f(x), so f is onto. Hence, f is one-oneand onto.