-10 1 8 + (-8 1 10 ) = -10 1 8 - 8 1 10 = -18 - 1 8 - 1 10 = -18 - 1 · 5 8 · 5 - 1 · 4 10 · 4 = -18 - 5 40 - 4 40 = - 18 - 5 + 4 40 = - 18 - 9 40 = -18 9 40 = -18.225. -18 9/40
-10 1 8 + (-8 1 10 ) = -10 1 8 - 8 1 10 = -18 - 1 8 - 1 10 = -18 - 1 · 5 8 · 5 - 1 · 4 10 · 4 = -18 - 5 40 - 4 40 = - 18 - 5 + 4 40 = - 18 - 9 40 = -18 9 40 = -18.225. -18 9/40