7𝑥 + 9 = −12 𝑥 = −3 𝑥2 + 4 𝑥 + 3 = 0 𝑥1 = −3
𝑥2 = −1
7𝑥 + 9 ≤ −12 𝑥 ≤ −3
𝑎, 𝑏
𝑥
(𝒂, 𝒃) = {𝒙 | 𝒂 < 𝒙 < 𝒃}
(𝑎, ∞) = {𝑥 | 𝑎 < 𝑥}
[𝒂, 𝒃] = {𝒙 | 𝒂 ≤ 𝒙 ≤ 𝒃}
(−∞, 𝑏) = {𝑥 | 𝑥 < 𝑏}
(𝒂, 𝒃] = {𝒙 | 𝒂 < 𝒙 ≤ 𝒃}
[𝑎, ∞) = {𝑥 | 𝑎 ≤ 𝑥}
[𝒂, 𝒃) = {𝒙 | 𝒂 ≤ 𝒙 < 𝒃}
(−∞, 𝑏] = {𝑥 | 𝑥 ≤ 𝑏}
7𝑥 + 9 ≤ −12 (−∞, 3]
𝑎≤𝑏 𝑎≤𝑏
𝑐>0
𝑎𝑐 ≤ 𝑏𝑐
𝑐
𝑎≤𝑏 𝑐<0 𝑎+𝑐 ≤ 𝑏+𝑐
7𝑥 + 9 ≤ −12
7𝑥 ≤ −21
𝑥≤−
21 = −3 7
(−∞, 3]
𝑎𝑐 ≥ 𝑏𝑐
𝑥 2 + 2𝑥 − 3 ≤ 0 𝑥 = −3 𝑥 = 1 𝑥 2 + 2𝑥 − 3 = (𝑥 + 3)(𝑥 − 1) ≤ 0
(𝑥 + 3)
(𝑥 − 1)
(𝑥 + 3)(𝑥 − 1) ≤ 0
(𝑥 + 3) ≤ 0
(𝑥 − 1) ≥ 0
(𝑥 + 3) ≥ 0
(𝑥 − 1) ≤ 0.
𝑥 ≤ −3
𝑥≥1
𝑥 ≥ −3
𝑥 ≤ 1. 𝑥 ∈ (−∞, −3] ∩ [1, ∞) 𝑥 ∈ [−3, ∞) ∩ (−∞, 1] 𝑥 ∈ ∅ ∪ [−3,1]
𝑥 ∈ [−3,1]
ЁЭСж = ЁЭСе 2 + 2ЁЭСе тИТ 3 ЁЭСе1 = тИТ3 [тИТ3,1]
ЁЭСе2 = 1