$a)u\left(x\right)-w\left(x\right)=\left(5x^9+2x^8+4x^4+2x+1\right)-\left(-2x^8-6x^4+\frac{3}{2}x-\frac{1}{2}\right)=$

$=5x^9+\underline{2x^8}+\underline{\underline{4x^4}}+\underline{\underline{\underline{2x}}}+\underline{\underline{\underline{\underline{1}}}}+\underline{2x^8}+\underline{\underline{6x^4}}-\underline{\underline{\underline{\frac{3}{2}x}}}+\underline{\underline{\underline{\underline{\frac{1}{2}}}}}=$  

$=5x^9+4x^8+10x^4+\frac{1}{2}x+1\frac{1}{2}$