2/(3a^2)+3/(4b)-5/(6ab)
=2*4b/(12a^2b)+3*3a^2/(12a^2b)-5*2a/(12a^2b)
=(9a^2-10a+8b)/(12a^2b)
(a+2b)/(a-b)+ b/(b-a)- 2a/(a-b)
=(a+2b)/(a-b)- b/(a-b)- 2a/(a-b)
={(a+2b)- b- 2a}/(a-b)
=-(a+b)/(a-b)
2/(3a^2)+3/(4b)-5/(6ab)
=2*4b/(12a^2b)+3*3a^2/(12a^2b)-5*2a/(12a^2b)
=(9a^2-10a+8b)/(12a^2b)
(a+2b)/(a-b)+ b/(b-a)- 2a/(a-b)
=(a+2b)/(a-b)- b/(a-b)- 2a/(a-b)
={(a+2b)- b- 2a}/(a-b)
=-(a+b)/(a-b)