Given: A line passing through the centre of circle x2+y2−16x−4y=0 which is (8,2) intersects positive x&y axis at A&B respectively,
So, let the line be ax+by=1
Now, given line passes through the centre,
So, a8+b2=1
Now, using A.M≥H.M we get,
62a+2a+2a+2a+1b+1b≥a2+a2+a2+a2+b1+b16
⇒62a+2b≥16
⇒2a+2b≥36
⇒a+b≥18
⇒OA+OB≥18
Hence, the minimum value of OA+OB=18