8500(1+x)2=7000 8500(1﹣x)2=7000
(6400﹣2000)(1+x)=6400 (6400﹣2000)(1+x)2=6400
(12400﹣5800)(1+x)=12400 (12400﹣5800)(1+x)2=12400
2000(1+x)2=3600
(3600﹣2000)(1+x)=3600
(3600﹣2000)(1+x)2=3600