21. Third term of an A.P. is four times the firstterm. If 6th term is

1.	21. Third term of an A.P. is four times the firstterm. If 6th term is 17 then its first termwill be:
Answer» Let a be the first term and D be the common differencethen a3=4aa+2d =4aa-4a+2d=0-3a+2d=03a-2d=0..........(i) and a6=17a+5d=17...........(ii) solving (i) &(ii), we geta=2 & d=3therefore A.P. is2,5,8,11,....... a3=a4; a+2d=4A,;a-4a+2d=0:; -3a+2d=0; 3a-2d=0_________(1); a6=17; a+5d=17, solving (i),(ii), a=2; d=3, A.P. is 2, 5, 8, 11, 14

21. Third term of an A.P. is four times the firstterm. If 6th term is 17 then its first termwill be:

Answer»

Let a be the first term and D be the common differencethen a3=4aa+2d =4aa-4a+2d=0-3a+2d=03a-2d=0..........(i)

and a6=17a+5d=17...........(ii)

solving (i) &(ii), we geta=2 & d=3therefore A.P. is2,5,8,11,.......

a3=a4; a+2d=4A,;a-4a+2d=0:; -3a+2d=0; 3a-2d=0_________(1); a6=17; a+5d=17, solving (i),(ii), a=2; d=3, A.P. is 2, 5, 8, 11, 14