#Mark the correct alternative in each of the following
The minimum value of f(x) = x4 – x2 – 2x + 6 is
f(x)=x4-x2-2x+6
f’(x)=4x3-2x-2
so here put f’(x)=0
4x3-2x-2=0
2(x-1)(2x2+2x+1)=0
x=1 and other roots are complex.
so we will consider x=1
Hence by second derivative test
f’’(x)>0 so it’s a point of minimum.
f”(x)=12x2-1
f” (1) =12(1)-2
=10>0
At x=1 minimum
So, f (1) =1-1-2(1) +6
=4
Option(B)