7(-3+2х)=-6х-1
-21+14х=-6х-1
14х+6х=-1+21
20х=20
х=1
|13 - 2x | ≥ |4x - 9|
(13 - 2x - (4x - 9))(13 - 2x + (4x - 9)) ≥ 0
(13 - 2x - 4x + 9)(13 - 2x + 4x - 9) ≥ 0
(22 - 6x)(2x + 4) ≥ 0
- 6(x - 22/6)* 2(x + 2) ≥ 0
(x - 11/3)(x + 2) ≤ 0
+ - +
_________[-2]________[3 2/3]____________
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Ответ : x ∈ [ - 2 ; 3 2/3]
Sina*cosa = 0.5*sin(2a)
sina + cosa = 4/3 - возведем обе части уравнения в квадрат
(sin^2(a) + 2sina*cosa + cos^2(a)) = 16/9
sin(2a) + 1 = 16/9
sin(2a) = (16/9) - 1 = 7/9
sina*cosa = 0.5*(7/9) = 7/18