(2-a)(4+2a+a²)-(3+a)(9-6a+a²)=
=8+4a+2a²-4a-2a²-a³-(27-18a+3a²+9a-6a²+a³)=
=8-a³-(a³-3a²-9a+27)=
=8-a³-a³+3a²+9a-27=
=-2a³+3a²+9a-19
Pri a=-2
-2(-8)+12-18-19= 16+12-18-10= -9
Х^2+y^2+2xy-4y-4x+4
б) 2x^2+y^2+4xy+4xz-4x+2zy-2y-2z+z^2+1
4/49 = (7/2)^-2
(7/2)^(x - 8 - x²) = (7/2)^-2
x - 8 - x² = -2
x² -x +6 = 0
По т. Виета х1 = 3 и х2 = -2