Cos3x*cosx+sin3x*sinx=cos2x
-1-9=-10
Х^2 = 9/16
x1 = 3/4
x2 = - 3/4
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x^2 = 16/49
x1 = 4/7
x2 = - 4/7
Y=-0,5x²+x+5,5 y=x²-2x+1
-0,5x²+x+5,5=x²-2x+1
1,5x²-3x-4,5=0 |÷1,5
x²-2x-3=0 D=16
x₁=-1 x₂=3
S=∫³₋₁(x²-2x+1+0,5x²-x-5,5)dx-∫³₋₁(1,5x²-3x-4,5)dx=(3x-3) |³₋₁=
=-3*3-3-(3*(-1)-3)=6-(-6)=6+6=12.
Ответ: S=12 кв. ед.