z a 9 + z 2 a 8 + z 3 a 7 − z a 7 + z 4 a 6 − 3 z 2 a 6 + 2 a 6 + z 3 a 5 − 2 z a 5 + z 4 a 4 − 4 z 2 a 4 + 3 a 4 {\displaystyle za^{9}+z^{2}a^{8}+z^{3}a^{7}-za^{7}+z^{4}a^{6}-3z^{2}a^{6}+2a^{6}+z^{3}a^{5}-2za^{5}+z^{4}a^{4}-4z^{2}a^{4}+3a^{4}}
