Question

the second term of a.p. is 15 and the fifth term is double the first. find first term and common difference an of a.p.

Answer 1

a2= 15= a+d......(i)

a5= 2a= a+4d
=2a-a=4d
=a = 4d......(ii)
putting the value of a in eq (i)

a+d=15
4d+d=15
5d=15
d=3

putting the value of d in eq (ii)
a=4d
a=12