In an A.P.the third term is four times the first term, and the sixth term is 17; find the series.

Answer 1

a+2d = 4a ---> 2d = 3a ----> a = 2d/3
sub that into
a+5d = 17
2d/3 + 5d = 17
17d/3 = 17
d = 3
then a = (2/3)(3) = 2

You don't specify how many terms you want in the series, but you should know the formula
Now that we know a and d, it is easy