9514 1404 393
Answer:
F20 = 15985k -20361g
Step-by-step explanation:
If we assume F3 and F4 are the third and fourth terms of an arithmetic sequence, the common difference is ...
d = F4 -F3 = (945k -713g) -(5k +515g)
d = 940k -1228g
Then the 20th term is ...
F20 = F3 +(20 -3)d = (5k +515g) +17(940k -1228g)
F20 = 15985k -20361g
