1/(a-b)+1/(b-c)+1/(c-a) =[(b-c)(c-a)+(a-b)(c-a)+(a-b)(b-c)]/(a-b)(b-c)(c-a) =[bc-ba-c²+ca+ac-a²-bc+ab+ab-ac-b²+bc]/(a-b)(b-c)(c-a) =[-(a²-ab+b²-ac+c²-bc)]/[-(a-b)(b...