SUBTRACTION. 275 



2x*y 24/^ — Zy i2*— 8+^* — 2 



• — 2xy* 3v ''^>-f'lo* ^ — 10+^* — X 



— 8a; ^jy — S+v/^j' lo — a — x^ — y 



SUBTRACTION. 



RULE/ 



Change each -j- into — , and each -— into 4** ^^ ^^^ 

 subtrahend, or suppose them to be thus changed j ther^ 

 proceed as in addition, and the sum will be the true re- 

 liiainder. 



EXA?.r?LES. 



* This rule is founded on the consideration, that addition and 

 subtraction are o^osite to each other in dieir nature and operation, 

 as are the signs -f- and — , by which they are expressed and rep- 

 resented. And since to unite a negative with a positive quantity 

 of the same kind has the effect of diminishing it, or subducting 

 an equal positive quantity from it ;. therefore to subtract a positive, 

 which is the opposite of uniting or adding, is to add the equal 

 negative quantity. Tn like manner, ta subtract a negative quan- 

 tity Is the same in effect, as to add or unite an equal positive 

 quantity. So that, by changing the sign of a quantity from -f- 

 to — , or from — to -{-, its nature is changed fronv a subductiv<i 

 to an additive quantity ; and any quan-Ity is in effect subtractet^ 

 by barely changing its sign. 



