Как то так...............
10sin38/sin19cos19 = 20sin38/sin38 = 20
Ответ: 20.
(2a-b)(a+b-c)-(a+2ab)(a-b+c)+3c(a+b)
2a²+2ab-2ac-ab-b²+bc-(a²-ab+ac+2a²b-2ab²+2abc)+3ac+3bc
2a²+2ab-2ac-ab-b²+bc-a²+ab-ac-2a²b+2ab²-2abc+3ac+3bc
a²+2ab-b²+4bc-2a²b+2ab²-2abc
Z²+13z+30=0
мо теореме Виета:
z1 + z2 = -13
z1z2 = 30
z1 = -3
z2 = -10
Ответ: -10; -3.
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