Question

sã se afle sirull de nr x-1330;x-1325;x-1320.al 6lea nr din șir este 8695.Determinã nr x;aflã al zecelea termen;suma primilor 3termeni

Answer 1

a1= x-1330
a2=x-1325
a3=x-1320
....
a6=8695

a1=x-(1330-5*0)
a2=x-(1330-5*1)
a3=x-(1330-5*2)
.............................
a6=8695
x- (1330-5*5)= 8695
x=(1330-25) +8695
x=1305+8695
x=10000
1.
a10=x-(1330-5*9)
a10=10000 - (1330-45)
a10=10000-1285
a10=8715
2.
a1+a2+a3= (10000-1330) +(10000-1325)+(1000-1320)=8670+8675+8680=
=8670*3+15=26025

Answer 2

x-1330,x-1325,x-1320,x-1315,x-1310,x-1305 

x-1305=8695       x=10 000

al zecilea termen=8695-20         al zecilea termen=8975!!!