Question

A g.p has 6 terms, if the 3rd and 4th terms are 28 and_56 respectively find :the first and the sum of the g.p

Answer 1

I don't know the workings pls help me out

Answer 2

https://www.mathsisfun.com/algebra/sequences-sums-geometric.html
or brute force
1
2
3 28
4 28 *r = 56 so r = 2
so the series is
1 7
2 14
3 28
4 56
5 112
6 224
now add :)