Ах-ау+5х-5у=a(x-y)+5(x-y)=(x-y)(a+5)
-4х+40=12х-12
-16х=-52
Х=52/16=3,25
Проверка
-4(3,25-10)=12*2,25
27=27 верно
Cos(arccos(a))=a, a∈[-1;1]
SinA-Sin3A 1/2 - 3*(1/2) 1/2 - 3/2 -2/2
--------------- = ---------------- = ------------- = -------- = -0,5 - Решение
Sin4A 4*(1/2) 4/2 4/2
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sinA = 1/2
X(y-5)-6y(5-y)=x(y-5)+6y(y-5)=(y-5)(x+6y)