\(\left(10-x^4+3x-4x^2\right)\left(2x+x^3-1\right)\)
\(\Rightarrow20x-2x^5+6x^2-8x^3+10x^3-x^7+3x^4-4x^5-10\)\(+x^4\) -3x\(+4x^2\)
\(\Rightarrow\left(-2x^5-4x^5\right)+\left(6x^2+4x^2\right)+\left(-8x^3+10x^3\right)\)\(+\left(-x^7\right)\) \(+\left(3x^4+x^4\right)\)+(20x-3x)+(-10)
=> \(-6x^5+10x^2+2x^3-x^7+4x^4+17x-10\)