$\begin{array}{l}\phantom{\phantom{;}a\phantom{;}-2;}{\phantom{;}a^{9}+2a^{8}+4a^{7}+8a^{6}+16a^{5}+32a^{4}+64a^{3}+128a^{2}+256a\phantom{;}+512\phantom{;}\phantom{;}}\\\phantom{;}a\phantom{;}-2\overline{\smash{)}\phantom{;}a^{10}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}-1024\phantom{;}\phantom{;}}\\\phantom{\phantom{;}a\phantom{;}-2;}\underline{-a^{10}+2a^{9}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{-a^{10}+2a^{9};}\phantom{;}2a^{9}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}-1024\phantom{;}\phantom{;}\\\phantom{\phantom{;}a\phantom{;}-2-;x^n;}\underline{-2a^{9}+4a^{8}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{;-2a^{9}+4a^{8}-;x^n;}\phantom{;}4a^{8}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}-1024\phantom{;}\phantom{;}\\\phantom{\phantom{;}a\phantom{;}-2-;x^n-;x^n;}\underline{-4a^{8}+8a^{7}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{;;-4a^{8}+8a^{7}-;x^n-;x^n;}\phantom{;}8a^{7}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}-1024\phantom{;}\phantom{;}\\\phantom{\phantom{;}a\phantom{;}-2-;x^n-;x^n-;x^n;}\underline{-8a^{7}+16a^{6}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{;;;-8a^{7}+16a^{6}-;x^n-;x^n-;x^n;}\phantom{;}16a^{6}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}-1024\phantom{;}\phantom{;}\\\phantom{\phantom{;}a\phantom{;}-2-;x^n-;x^n-;x^n-;x^n;}\underline{-16a^{6}+32a^{5}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{;;;;-16a^{6}+32a^{5}-;x^n-;x^n-;x^n-;x^n;}\phantom{;}32a^{5}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}-1024\phantom{;}\phantom{;}\\\phantom{\phantom{;}a\phantom{;}-2-;x^n-;x^n-;x^n-;x^n-;x^n;}\underline{-32a^{5}+64a^{4}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{;;;;;-32a^{5}+64a^{4}-;x^n-;x^n-;x^n-;x^n-;x^n;}\phantom{;}64a^{4}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}-1024\phantom{;}\phantom{;}\\\phantom{\phantom{;}a\phantom{;}-2-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n;}\underline{-64a^{4}+128a^{3}\phantom{-;x^n}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{;;;;;;-64a^{4}+128a^{3}-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n;}\phantom{;}128a^{3}\phantom{-;x^n}\phantom{-;x^n}-1024\phantom{;}\phantom{;}\\\phantom{\phantom{;}a\phantom{;}-2-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n;}\underline{-128a^{3}+256a^{2}\phantom{-;x^n}\phantom{-;x^n}}\\\phantom{;;;;;;;-128a^{3}+256a^{2}-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n;}\phantom{;}256a^{2}\phantom{-;x^n}-1024\phantom{;}\phantom{;}\\\phantom{\phantom{;}a\phantom{;}-2-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n;}\underline{-256a^{2}+512a\phantom{;}\phantom{-;x^n}}\\\phantom{;;;;;;;;-256a^{2}+512a\phantom{;}-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n;}\phantom{;}512a\phantom{;}-1024\phantom{;}\phantom{;}\\\phantom{\phantom{;}a\phantom{;}-2-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n;}\underline{-512a\phantom{;}+1024\phantom{;}\phantom{;}}\\\phantom{;;;;;;;;;-512a\phantom{;}+1024\phantom{;}\phantom{;}-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n-;x^n;}\\\end{array}$

$a^{9}+2a^{8}+4a^{7}+8a^{6}+16a^{5}+32a^{4}+64a^{3}+128a^{2}+256a+512$