2) , a 3 = 2 a 5= -2.
. ,
a 3 = a 1+ 2 d, | |
a 5 = a 1+ 4 d, |
, ,
a 1+ 2 d = 2, | |
a 1+ 4 d = -2, |
= 6 d = -2.
3) , 3.
. , 3, 102. , 3, 6,
102, 108, 114,..., 996,
a 1 = 102, d = 6 ax = 996 (x N).
ax = a 1 + (x - 1) d
102 + (x - 1)6 = 996,
x = 150. , n ,
4) , , 2, 5, 8,..., 332 7, 12, 17,..., 157.
. b - n - , ,
b = 2 + (n - 1)3 , , b m - , , b = 7 + (m - 1)5. ,
2 + (n - 1)3 = 7 + (m - 1)5,
3(n - 1) = 5 m
, , m, n - , n = 5 k + 1 m = 3 k, k Î N, , a 6, a 11, a 16,..., a 5 k +1 c 3, c 6, c 9,..., c 3 k, . , 17, 32, 47, 62, 77, 92, 107, 122, 137 152 .
. .