Степень 7 ............................
![\left \{ {{x+2y=4} \atop {3x-4y=2}} \right. \ =\ \textgreater \ x=4-2y](https://tex.z-dn.net/?f=+%5Cleft+%5C%7B+%7B%7Bx%2B2y%3D4%7D+%5Catop+%7B3x-4y%3D2%7D%7D+%5Cright.++%5C+%3D%5C+%5Ctextgreater+%5C++x%3D4-2y)
подставляем во второе ур-е
![3(4-2y)-4y=2 \\ 12-6y-4y=2 \\ 10y=10 \\ y=1 \\ \\ x=4-2y \\ x=4-2*1 =4- 2= 2](https://tex.z-dn.net/?f=3%284-2y%29-4y%3D2+%5C%5C+12-6y-4y%3D2+%5C%5C+10y%3D10+%5C%5C+y%3D1+%5C%5C++%5C%5C+x%3D4-2y+%5C%5C+x%3D4-2%2A1+%3D4-+2%3D+2+)
y=1
x=2
![\left \{ {{2x-3y=2} \atop {4x-5y=1}} \right. \ =\ \textgreater \ 2x=2+3y](https://tex.z-dn.net/?f=+%5Cleft+%5C%7B+%7B%7B2x-3y%3D2%7D+%5Catop+%7B4x-5y%3D1%7D%7D+%5Cright.+%5C+%3D%5C+%5Ctextgreater+%5C+2x%3D2%2B3y)
![x= \frac{2+3y}{2}](https://tex.z-dn.net/?f=x%3D+%5Cfrac%7B2%2B3y%7D%7B2%7D+)
![4x-5y=1 \\ \\ 4(\frac{2+3y}{2} )-5y=1 \\ 2(2+3y)-5y=1 \\ 4+6y-5y=1 \\ y=-3 \\ \\ x= \frac{2+3y}{2} \\ x= \frac{2+3*(-3)}{2}= -\frac{7}{2}](https://tex.z-dn.net/?f=4x-5y%3D1+%5C%5C++%5C%5C+4%28%5Cfrac%7B2%2B3y%7D%7B2%7D+%29-5y%3D1+%5C%5C+2%282%2B3y%29-5y%3D1+%5C%5C+4%2B6y-5y%3D1+%5C%5C+y%3D-3+%5C%5C++%5C%5C+x%3D+%5Cfrac%7B2%2B3y%7D%7B2%7D++%5C%5C+x%3D+%5Cfrac%7B2%2B3%2A%28-3%29%7D%7B2%7D%3D+-%5Cfrac%7B7%7D%7B2%7D++)
y=-3
x=-7/2
Sin(π+x) = -sinx
cos(π/2 - x) = sinx
sinx - sinx - 2sinx = 1
sinx = -1/2
x = -π/6 + 2πk, k∈Z
x = -5π/6 + 2πk, k∈Z
В первой и третьей.
при х больше нуля - у больше нуля;
при х меньше нуля - у меньше нуля так как х в нечетной степени.
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