Tuesday

October 25, 2016
Posted by **Lucas** on Sunday, February 3, 2013 at 12:08pm.

- Maths -
**Steve**, Sunday, February 3, 2013 at 2:36pma+d = ar

3/2 (2a+2d) = ar^2

3a+3d = ar^2

3(a+d) = ar^2

3ar = ar^2

3r = r^2

r = 3

So,

a+d = 3a

d = 2a

The sequences are thus

a,3a,5a,7a,9a,...

a,3a,9a,27a,...

Note that a+3a+5a = 9a, as required

Pick a value for a, and plug and chug.