The quadratic formula for \(ax^2 + bx + c = 0\) is \[x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\] which is a standard result in algebra.
Moduli stacks of etale (phi,Gamma)-modules and the existence of crystalline lifts
Moduli stacks of (phi,Gamma)-modules: a survey
John Voight's note on stacks
Jarod Alper's course on stacks
Emerton and Gee's paper: "
scheme-theoretic images" of morphisms of stacks
Pappas & Rapoport's paper: Phi-modules and coefficient spaces
Aug. 24th, 2022