a: \(P\left(x\right)=2x^2-4x-1\)
\(Q\left(x\right)=-4x^3-3x^2-4x-2\)
b: \(A\left(x\right)=P\left(x\right)+Q\left(x\right)\)
\(=2x^2-4x-1-4x^3-3x^2-4x-2\)
\(=-4x^3-x^2-8x-3\)
\(B\left(x\right)=P\left(x\right)-Q\left(x\right)\)
\(=2x^2-4x-1+4x^3+3x^2+4x+2\)
\(=4x^3+5x^2+1\)