Решение во вложенииииииииииииииииииииииииииии
Y7 = 9 - 5•7 = 9 - 35 = -26
y8 = 9 - 5•8 = -31
y2k = 9 - 5•2k = 9 - 10k
y2k-1 = 9 - 5(2k - 1) = 9 - 10k + 5 = 14 - 10k.
-86 = 9 - 5n
-86 - 9 = -5n
n = 19.
1)180(n-2)/n<30
(180n-360)/n-30<0
(180-360-30n)/n<0
(150n-360)/n<0
n=0 U n=2,4
n∈(0;2,4)
n=2
2)a{-4;9}
b{8;3}
a+b{4;12}
(/a+b/)²=16+144=160
3sinx-4cosx=5
3sinx+4cosx= -5 Делим на 5
3/5sinx+4/5cosx=-1
sin(x+ arcsin4/5) = -1
x+arcsin4/5 = -pi/2+2pi*k
x= -pi/2+2pi*k - arcsin4/5