Перемножаем :
9my^2-2ny^2-27my-6ny+81m-18n -y^3 +2y
33+3(6х-5у)^2+3(x+2y)^2-5y= 36(36x^2-60xy+25y)+3(2x^2+4xy+4y)-5y =
1296x^2-2160xy+900y+6x^2+12xy+12y-5y=1302x^2-2148xy+907y
2ax/(a+x)(a-x)-x/(a+x)=2ax-x(a-x)/(a-x)(a+x)=(x^2+ax)/(a-x)(a+x)=x/a-x
Y=x-4
x^2+x-4+4=0
x^2+x=0
x(x+1)=0
x=0 y=-4
x=-1 y=-5