a14 = a1 + 13 d = 864
a25 = a1 + 24 d = 1557
a25 - a14
a1 + 24 d = 1557
-
a1 + 13 d = 864
____________
11 d = 693
d = 693 / 11
d = 63
Replace this value in equation:
a1 + 13 d = 864
a1 + 13 ∙ 63 = 864
a1 + 819 = 864
a1 = 864 - 819
a1 = 45
a19 = a1 + 18 d = 45 + 18 ∙ 63 = 45 + 1134 = 1179
a6 = a1 + 5 d = 45 + 5 ∙ 63 = 45 + 315 = 360
a13 = a1 + 12 d = 45 + 12 ∙ 63 = 45 + 756 = 801
a56 = a1 + 55 d = 45 + 55 ∙ 63 = 45 + 3465 = 3510
a13 + a56 = 801 + 3510 = 4311
a6 ∙ a13 = 360 ∙ 801 = 288360
The 14th term of an A.P is 864,while 25th term is 1557 find the ,19th term,sum of 13th and 56th terms,product of 6th and 13th terms.
1 answer