(9/10-1/8*u⁸)²=81/100-(9/40u⁸+(1/64)u¹⁶)
c⁸−d¹⁰=(c⁴−d⁵)(c⁴+d⁵)
(c+19d)²−(19c+d)²=(c+19d-19c-d)(c+19d+19c+d)=(18d-18c)(20d+20c)=360(d-c)(d+c)
(9/10-1/8*u⁸)²=81/100-(9/40u⁸+(1/64)u¹⁶)
c⁸−d¹⁰=(c⁴−d⁵)(c⁴+d⁵)
(c+19d)²−(19c+d)²=(c+19d-19c-d)(c+19d+19c+d)=(18d-18c)(20d+20c)=360(d-c)(d+c)