(1/8z^5 - 7/8)^2 = (1/8z^5 - 7/8)(1/8z^5 - 7/8= (1/8z^5)(1/8z^5) + (1/8z^5)(-7/8) - (7/8)(1/8z^5) - (7/8)(7/8= 1/64z^10 - 7/64z^5 - 7/64z^5 + 49/6= 1/64z^10 - 14/64z^5 + 49/6= 1/64z^10 - 7/32z^5 + 49/64.
(1/8z^5 - 7/8)^2 = (1/8z^5 - 7/8)(1/8z^5 - 7/8
= (1/8z^5)(1/8z^5) + (1/8z^5)(-7/8) - (7/8)(1/8z^5) - (7/8)(7/8
= 1/64z^10 - 7/64z^5 - 7/64z^5 + 49/6
= 1/64z^10 - 14/64z^5 + 49/6
= 1/64z^10 - 7/32z^5 + 49/64.