Arithmetica Universalis
As if 12 Oxen in 4 Weeks eat up 3+1/3 Acres, then by Proportion 36 Oxen in 4 Weeks, or 16 Oxen in 9 Weeks, or 8 Oxen in 18 Weeks, will eat up 10 Acres, on Supposition that the Grass did not grow. But since by reason of the Growth of the Grass 21 Oxen in 9 Weeks can eat up only 10 Acres, that Growth of the Grass in 10 Acres for the last 5 Weeks will be as much as would be sufficient to feed 5 Oxen, that is the Excess of 21 above 16 for 9 Weeks, or, what is the same Thing, to feed 5/2 Oxen for 18 Weeks.
以下に複素数根の個数について該当する記述を引用する。
CXIX. Where there are none of the Roots of the Equation impossible, the Number of the affirmative and negative Roots may be known from the Signs of the Terms of the Equation. For there are so many affirmative Roots, as there are Changes of the Signs in continual Series from + to −, and from − to +; the rest are negative. As in the Equation x − x − 19xx + 49x − 30 = 0, where the Signs of the Terms follow one another in this Order, + − − + −, the Variations of the second − {\displaystyle -} from the first + {\displaystyle +} , of the fourth + {\displaystyle +} from the third − {\displaystyle -} , and of the fifth − {\displaystyle -} from the fourth + {\displaystyle +} , shew, that there are three affirmative Roots, and consequently, that the fourth is a negative one.