f(x)=[x2−x+1]+∣x2−x+1∣x∈[−1,2]
∵∣x2−x+1∣→(x2−x+1)>0
∴f(x)=(x2−x+1)+[x2−x+1]
Now,
Consider g(x)=(x2−x+1)
For the minimum value of g(x),
g′(x)=0⇒2x−1=0
⇒x=21
(x2−x+1) attains its minimum value at x=21
And min[x2−x+1]=0asx2−x+1>0
⇒f(x) attains its minimum at x=21
So, f(21)=43+0=43