№1 а6=45 а14=-43 найти s10 № 2 а1=10 s14=1050 найти: d

1) a6=a1+5d=45a14 = a1+ 13d = -43a1+13d-a1-5d=-43-458d=-88d=-11a1=45-5d=45+55=100s10 = (2a1+9d)/2 * 10 = (2a1+9d)5 = (200-99)*5=101*5=5052) s14 = (2a1+13d)/2 * 14 = (2a1+13d)*7 = 1050(20+13d)*7=105020+13d = 15013d=130d=10 

(-1,21)²=1,4641

1,4641> 0

{а1+11d=6

{a1+23d=12

{a1=6-11d

{6-11d+23d=12

12d=12-6

12d=6

d=6: 12

d=0,5

a1=6-11d=6-11*0,5=6-5,5=0,5

a18=a1+17d=0,5+17*0,5=9