Question

Find 100 is a term of ap 25,28,31..... Or not

Answer 1

an=100 ; a=25 ; d=3
100=25+(n-1)3
100=25+3n-3
100=22+3n
3n=78
n=26.
yes,100 is 26th term of AP.

Answer 2

an = 100
a   =  25
d   =   3
                       an = a+(n-1)d
                     100 = 25 + (n-1)3
                     100 = 25 +3n -3
                     100 = 22 + 3n
                      78  = 3n
                        n  = 78/3
                        n  =  26
 therefore 100 is a term of AP 25,28,31..........