( 8 - 7X)*( 8 + 7X) > 0
------------------------
8 - 7X > 0
8 > 7X
8/7 > X
X < 8/7
X < 1 1/7
----------------------
8 + 7X > 0
7X > - 8
X > - 1 1/7
-------------------
Ответ Х ∈ ( - 1 1/7 ; 1 1/7 )
300 грамм, 3525кг , 408кг
(32-7n)+(64+17n)=19-(6n-13)
32-7n+64+17n=19-6n+13
17n-7n+6n=19+13-32-64
16n= -64
n=-64:16
n=- 4
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