Q5 of 137 Page 19

#Mark the correct alternative in each of the following

Let f(x) = x3 + 3x2 – 9x + 2. Then f(x) has


f(x)=x3+3x2-9x+2


f’(x)=3x2+6x-9


f’(x)=0


3x2+6x-9=0


by solving the quadratic we get roots as follows


x=-3 and x=1


Hence by second derivative test


f’’(x)>0 or f”(x)<0 so it’s a point of minimum or maximum respecctively.


f”(x)=6x+6


f”(-3)=6(-3)+6


=-12<0


so At x=-3 maximum value.


f”(1)=6+6


=12>0


so At x=1 minimum value.


Option=(B)

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