272 



CASE II. 

 When like quantities have iinlihe signs » 



RULE. 



Subtract the less coefficient from the greater, to the re- 

 mainder prefix the sign of the greater, and annex their 

 common letters or quantities. 



EXAMPLES. 



V ^' ^- 3-* 4- S'_ 



To +6a — 7^ ■ +2C — cd -hSs/a'+b^ 



Add — 2a +6b — 2c +2cd — 8^^^^+^ 



Sum +4^ b * +2ed 5\/a^+b' 



* In example 3, the coefficients of the two quantities, viz. 

 4-2C and — 2c, are equal to each other, therefore tliey destroy 

 one another, and so their sum makes o, or #, which is frequently 

 used, in algebra, to signify a vacant place. 



