# How do you divide (3x^3 + 5x^2 -3 x + 15) / (3x^2 -4x+12)?

I tried to explain as much as possible the division where I got $\left(x + 3\right)$ with a remainder of $- 3 x - 21$:
From the picture, I divide the first time and got $x$ and then (after subtracting and using $15$) I divide again and got $+ 3$.