4th term of an A. P. is equal to 3 times its first term 7th term exceeds twice the 3rd term by 1. Find the first term and the common difference.
Given a4=3a1i.e,(a+3d)=3aHence,2a=3d∴,a=3d2Also given that a7=2a3+1(a+6d)=2(a+2d)+1a+6d=2a+4d+1a=2d–13d2=2d–1d2=1∴,d=2a=3d2=3