The two circles x2+y2=axandx2+y2=c2(c>0) touch each other if
If two circles touch each other
⟹r1+r2=c1c2 (externally)
Or
⟹|r1–r2|=c1c2 (internally)
⟹a+c=a
But c≠0
|a−c|=a
⟹c≠0,c=2|a|
Correct answer is c≠0,c=2|a|