a)= 8x⁷-12x⁴
b)=2x⁶-x³-6x⁴+3x
c)=x²-x+4(x²+x-2x-2)=x²-x+4(x²-x-2)=x²-x+4x²-4x-8=5x²-5x-8
d)=3y²-2x²-4xy-2x²-xy+2xy+y²=-4x²+4y²-3xy
