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

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

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

$st\left(u\right)=9$  

$st\left(w\right)=8$  

$st\left(u-w\right)=9$  

 

 

 

$b)u\left(x\right)-w\left(x\right)=\left(\frac{3}{4}{x}^6+\frac{1}{5}{x}^4-\frac{3}{8}{x}^2+1\right)-\left(0,75x^6-0,2x^4+0,125x^2\right)=$  

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

$=\frac{2}{5}{x}^4-\frac{1}{2}{x}^2+1$  

 

$st\left(u\right)=6$  

$st\left(w\right)=6$  

$st\left(u-w\right)=4$