Let P(x1,x12)
Minimum distance will be obtained at common normal of the parabola and circle.
So for minimum PQ, the distance between centre of circle and P should be minimum.
Now, the distance of P from given circle,
d=(x1−1)2+(x12+1)2−1
For least value of d, we need to minimize
f(x1)=(x1−1)2+(x12+1)2
i.e. f′(x1)=2(x1−1)+4x1(x12+1)=0
From options
f′(41) is −ve and f′(21) is +ve
So, f′(x1)=0 for some x1∈(41,21) from IMVT