1)Имеем:
-2sin x = -1
sin x = 1/2
x = (-1)^k * arcsin 1/2 + πk, k∈ Z
x = (-1)^k * π/6 + πk, k ∈ Z
2) -1 ≤ sin x ≤ 1
-2 ≤ 2sin x ≤ 2
3 ≤ 5 + sin 2x ≤ 7
Значит, множеством значений функции является отрезок [3;7]
x = y - 5/7
4y - 20/7 + 3y = -34/7
7y = 14/7
y = 2/7
x = 2/7 - 5/7 = -3/7
b) y = 10/21 + x
9x + 20/21 + 2x = -19/7
11x = -57/21 - 20/21
11x = -77/21
x = - 7/21
y = 10/21 - 7/21 = 3/21 = 1/7