Prove that the function f given by f (x) = x2 – x + 1 is neither strictly increasing nor strictly decreasing on (– 1, 1).


It is given that function f(x) = x2 – x + 1

f’(x) = 2x – 1


If f’(x) = 0, then we get,


x =


So, the point x = divides the interval (-1,1) into two disjoint intervals,



So, in interval


f’(x) = 2x – 1 < 0


Therefore, the given function (f) is strictly decreasing in interval


So, in interval


f’(x) = 2x -1 > 0


Therefore, the given function (f) is strictly increasing in interval for.


Therefore, f is neither strictly increasing and decreasing in interval (-1,1).


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