A1+a2+a3+a4=100
a1,a1+d,a1+2d,a1+3d
a1+a1+d+a1+2d+a1+3d=100
4a1+6d=100
2a1+3d=50
sn=n/2(a1+an) -eto formula
100=4/2(a1+a1+3d),100=2.(2a1+3d)
2.10+3.10=50,d=10
a1=10,a2=20,a3=30,a4=40
Octalnye rešenija:
a1=4,a2=18,a3=32,a4=46,d=14
a1=16,a2=22,a3=28,a4=34, d= 6
a1=22,a2=24,a3=26,a4=28, d=2
-2 =4х
х =4 ÷2=2
5=0,2х
х =0.2÷5