If the function f(x) = cos |x| -2ax + b increases for all x ∈ R, then
Answer & explanation
Correct answer: option 3
Here $f'(x) ≥ 0, ∀x ∈ R$
$⇒ -sinx - 2a ≥ 0, ∀x ∈ R$
$⇒ a ≤ -\frac{sinx}{2} ⇒ a ≤ -\frac{1}{2}$.
Hence (C) is the correct answer.
If the function f(x) = cos |x| -2ax + b increases for all x ∈ R, then
Correct answer: option 3
Here $f'(x) ≥ 0, ∀x ∈ R$
$⇒ -sinx - 2a ≥ 0, ∀x ∈ R$
$⇒ a ≤ -\frac{sinx}{2} ⇒ a ≤ -\frac{1}{2}$.
Hence (C) is the correct answer.