Given,
The centre of a circle C be α,β and its radius r<8,
And 3x+4y=24 and 3x–4y=32 be two tangents
So, the distance from centre will be radius,
∣53α+4β−24∣=∣53α−4β−32∣
Taking + sign we get,
⇒3α+4β−24=3α−4β−32
⇒8β=−8⇒β=−1
And taking − sign we get,
3α+4β−24=−3α+4β+32
⇒6α=56⇒α=656
And 4x+3y=1 be a normal to C
So, (α,β) lies on 4x+3y=1
⇒4α+3β=1
So, α=1 when β=−1 and β=31(1−4×328)=9−109,ifα=328
Hence, radius will be,
r=∣53−4−24∣=5<8 if (α,β)=(1,−1)
And if (α,β)=(328,9−109) then r>8, so neglected.
∴r=5,α=1,β=−1
∴α−β+r=7