\(a,A=x^2\left(x-y^2\right)-xy\left(1-yx\right)-x^8\\ =x^3-x^2y^2-xy+x^2y^2-x^8=x^3-xy-x^8\\ b,B=x\left(x+3y+1\right)-2y\left(x-1\right)-\left(y+x+1\right)x\\ =x^2+3xy+x-2xy+2y-xy-x^2-x\\ =\left(x^2-x^2\right)+\left(3xy-2xy-xy\right)+\left(x-x\right)+2y=2y\)


