z 3 a 7 − z a 7 + 2 z 4 a 6 − 2 z 2 a 6 + a 6 + 2 z 5 a 5 − z 3 a 5 + z 6 a 4 + 2 z 4 a 4 − 4 z 2 a 4 + 2 a 4 + 4 z 5 a 3 − 6 z 3 a 3 + 2 z a 3 + z 6 a 2 + z 4 a 2 − 4 z 2 a 2 + a 2 + 2 z 5 a − 4 z 3 a + z a + z 4 − 2 z 2 + 1 {\displaystyle z^{3}a^{7}-za^{7}+2z^{4}a^{6}-2z^{2}a^{6}+a^{6}+2z^{5}a^{5}-z^{3}a^{5}+z^{6}a^{4}+2z^{4}a^{4}-4z^{2}a^{4}+2a^{4}+4z^{5}a^{3}-6z^{3}a^{3}+2za^{3}+z^{6}a^{2}+z^{4}a^{2}-4z^{2}a^{2}+a^{2}+2z^{5}a-4z^{3}a+za+z^{4}-2z^{2}+1}
