Q. 55.0( 1 Vote )

# Mark the correct alternative in the following:If the function f(x) = 2x2 – kx + 5 is increasing on [1, 2], then k lies in the interval.A. (–∞, 4)B. (4, ∞)C. (–∞, 8)D. (8, ∞)

Formula:- The necessary and sufficient condition for differentiable function defined on (a,b) to be strictly increasing on (a,b) is that f’(x)>0 for all x(a,b)

f(x) = 2x2 – kx + 5

f(x)>0

4x-k>0

K<4x

For x=1

K<4

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