
The length of the perpendicular from centre (0,0) to the line x+y=n is ∣12+I20+0−n∣=2n
Length of intercept =242−(2n)2=64−2n2
⇒ Possible values of n are 1,2,….5
⇒ Sum of the square of lengths of intercepts
=Σn=15(64−2n2)=64×5−2Σn=15n2
=320−2Σn=15n2=320−110=210