Question

The third,fourth and eight term of A.P form first three consecutive term of G.P.if the sum of the first ten term of A.P is 85.calculate the first term of both A.P and G.P,common ratio and sum of 5 term of G.P

Answer 1

a = 1st term A.P. ... d = common difference

10 a + 45 d = 85 ... 2 a + 9 d = 17

(3a + 3d) / (4a + 6d) = (4a + 6d) / (8a + 28d)

two equations and two unknowns

Answer 2

(4a + 6d) (8 a + 28d)

Answer 3

Helpful for the Answer on qn above