Let k and K be the minimum and the maximum values of the function f x = 1 + x 0.6 1 + x 0.6   in  …

Let k and K be the minimum and the maximum values of the function fx=1+x0.61+x0.6 in 0, 1, respectively, then the ordered pair (k, K) is equal to:
  1. 2-0.4,1
  2. 2-0.6, 1
  3. 2-0.4,20.6
  4. 1,20.6

Solution

fx= 1+x0.61+x0.6

fx= 0.61+x-0.4 1+x0.6-0.6 x0.41+x0.61+x0.62

=0.6 1+x-0.4 1+x0.6-x-0.4 1+x21+x0.62=0.6x0.4-11+x0.41+x0.62

Clearly it is always negative in [0, 1]

minimum value would be at x=1.

(1+1)0.61+10.6= 20.62=2-0.4=k

& maximum values would be at x=0

(1+0)0.61+00.6=11=K

Hence 2-0.4,1

Asked in: JEE Main 2015 (11 Apr Online)

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