a)
Ta có: \(2x\left(x^2-x-1\right)=2x^3-2x^2-2x\)
b)
Ta có: \(\left(x-1\right)^2+\left(x+1\right)^2=x^2-2x+1+x^2+2x+1=2x^2+2\)
c)
Ta có: \(\frac{\left(4x^2-9y^2\right)}{2x-3y}=\frac{\left(2x-3y\right)\left(2x+3y\right)}{2x-3y}=2x+3y\)
d)
Ta có: \(\left(x-2\right)\left(x^2+2x+4\right)-x\left(x^2-3\right)=x^3-8-x^3+3x=-8+3x\)