I'm just a little confused about dy/dx. I read that its one entity not a fraction. Can someone please clarify why is this not a fraction? According to what I know (delta y)/(delta x) becomes equal to dy/dx as (delta x) appraches zero. If delta x apparaches to zero then delta y should alway have some value. We are also solving differential equations in our class. In first order diffential eq. we take the dx and terms in x to one side of equation and the terms in y and dy on other side and then integrate both side. Doesnt that show that dy/dx IS infact a fraction? Thanks in advance for any help. PS: I'm sorry for my bad english. .