first term: a
2nd term a+d and ar
so, a+d = ar
r = 1 + d/a
So, pick an a&d, say 1&2.
AP: 1,3,5,7,9...
GP: 1,3,9,27,81,...
or, 10&5:
AP: 1,11,21,31,...
GP: 1,11,121,1331,...
If no other information is given, that's about as far as we can go.
An arithmetic progression as the same first and second terms as the geometric progression. Find the sum of the first 20 terms of the arithmetic progression.
How do I do this? I tried to find the common ratio for G.P. and then substitute it to find the 20th term but, still have 2 unknown terms. Please help!
1 answer