Illustration 6.4 Find the least value ofk for which the functionr+kx+ – InterviewSolution

1.

Illustration 6.4 Find the least value ofk for which the functionr+kx+ 1 is an increasing function in the interval 1 <x<2(NCERT)

Answer»

f(x) = x^2+ kx + 1

f'(x) = 2x + k >= 0 if f(x) is increasing

Or,

k>= -2x

Now x ε (1,2)

thus,

k>= -2

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