Hello, I am currently in my first year of college, and I already took calculus in high school. I was able to solve all the problems, but I feel like I didn't understand everything conceptually. When integrating dy/dx=x you get, ∫x dx=1/2x2. But what exactly happened to the dx, why did it disappear? I thought that dx was an infinitesimally small number, representing the width of the rectangles in a Riemann Sum. Also, I tried solving this question geometrically, but I think that I might be doing something wrong. Starting from any point x, and using left endpoint rectangles, I got that the heights of the rectangles are x,x+dx,x+2dx,... And the width is just dx. So the area under the curve y=x is dx(x+(x+dx)+(x+2dx)+(x+3dx)...) which is equal to: dx(x+x+x...+dx(1+2+3+4...))? Am I misinterpreting dx or can I simplify this sum even further to get 1/2x2? Thank you.