d = 4
Объяснение:
a1 = 3; S(22) = 990; d = ?
S(22) = (2a1 + d*21)*22/2
(2*3 + 21d)*11 = 990
6 + 21d = 90
21d = 90 - 6 = 84
d = 84 : 21 = 4
d = 4
Объяснение:
a1 = 3; S(22) = 990; d = ?
S(22) = (2a1 + d*21)*22/2
(2*3 + 21d)*11 = 990
6 + 21d = 90
21d = 90 - 6 = 84
d = 84 : 21 = 4