Q.

f(x) = 4 loge(x1)2x2+4x+5,x>1which one of the following is NOT correct ?

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a

f(x)= -1 has exactly two solutions

b

f(x) = 0has a root in the interval (e, e +1)

c

f is increasing in (1, 2) and decreasing in (2, ∞)

d

f(e)f′′(2)<0

answer is C.

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Detailed Solution

f(x)=4loge(x1)2x2+4x+5,x>1f(x)=4x14(x1)
For 1<x<2f'(x)>0
For x>2f'(x)<0    (option 1 is correct)
f(x) = -1 has two solution    (option 2 is correct)
f(e)>0f(e+1)<0f(e)f(e+1)<0          (option 4 is correct) f '(e)f ''(2)=4e14(e1)+8>0
(option C is incorrect)

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