A₁ = - 79 a₂ = - 61
a₂ = a₁ + d
d = a₂ - a₁ = - 61 - (- 79) = - 61 + 79 = 18
Решение смотри в приложении
2Cos²2x + Cos2x = 0
Cos2x(2Cos2x +1) = 0
Cos2x = 0 или 2Cos2x +1 = 0
2x = π/2 + πk , k ∈Z Cos2x = -1
x = π/4 + πk/2, k ∈Z 2x = π +2πn, n ∈Z
x = π/2 + πn, n ∈Z
A)0,26x-0,05(x-3)=0,06x
0,26x-0,05x-0,06x=-0,15
0,15x=-0,15
x=-1
b)0,12+0,76x=0,66(x+1)
0,76x-0,66x=0,66-0,12
0,1x=0,54
x=5,4