SaraNextGen.Com

Let f : [0, 2] → R be a twice differentiable function such that f ’(x) > 0, for all x  (0, 2). If (x) = f(x) + f(2 − x), then  is

(a) Decreasing on (0, 2)

(b) Increasing on (0, 2)

(c) Decreasing on (0, 1) and increasing on (1, 2)

(d) Increasing on (0, 1) and decreasing on (1, 2)



Question ID - 57548 | SaraNextGen Top Answer

Let f : [0, 2] → R be a twice differentiable function such that f ’(x) > 0, for all x  (0, 2). If (x) = f(x) + f(2 − x), then  is

(a) Decreasing on (0, 2)

(b) Increasing on (0, 2)

(c) Decreasing on (0, 1) and increasing on (1, 2)

(d) Increasing on (0, 1) and decreasing on (1, 2)

1 Answer
127 votes
Answer Key / Explanation : (c) -

(x) = f(x) + f(2 − x)

differentiating w.r.t. x

’(x) = f ’(x) − f ’(2 − x)

For (x) to be increasing ’(x) > 0

⇒ f ’(x) > f ’(2 − x)

(\because f ’’(x) > 0 then f ’(x) is an increasing function)

⇒ x > 2 − x

⇒ x > 1

So (x) is increasing in (1, 2) and decreasing in (0, 1)

127 votes


127