Prove that f (x) = ax + b, where a and b are constants and a > 0 is an strictly increasing function for all real values of x. without using the derivative.
Here f (x) = 4x3 – 6x2 + 3x + 12 12 ∴ Df = R
f ' (x) = 12x2 – 12x + 3 = 3(2x – 1)2 4x + 1) = 3(2 x – 1)2 ≥ 0 ∀ x ∊ R
∴ f (x) is increasing on R.
Prove that the function f (x) = sinx is
(i) strictly increasing in
(ii) strictly decreasing in
(iii) neither increasing nor decreasing in .
Prove that the function f (x) = cos x is
(i) strictly increasing in
(ii) strictly decreasing in
(iii) neither increasing nor decreasing in