Hey guys, Question here.

I have been learning about re-topology recently and it has absolutely changed the way i model and the ease at which i can deal with problems later down the line in my process. given this though, there are some things about the ideal geometry i am looking for that i don't know how to accomplish when it comes to the basics. I have included a photo, where a cylinder meets a block. upon boolean'ing them together, i will pull off the cylinder part and rebuild the cube with the edges left behind. if i extrude the blue edges to where the yellow vertices are (the vertices don't already exist, they are depicted as what i expect to create if i extrude the blue line), then the face on the right side of the photo would have multiple points on one edge, making it an n-gon instead of a 4 sided polygon. how can i extrude the blue line to create the square geometry, without having a line cut with multiple points. i have seen techniques where some people double back the edges to themselves but in this specific situation I'm not sure what to do.

Also, if anyone knows any foundation geometry modeling guides, that would be very helpful. I'm looking for a "when you want to make this type of corner, do this" type of deal.