· Vikram Aruchamy · LaTeX
How to Add Line Breaks in LaTeX Equations (amsmath Guide)
To break a long equation in LaTeX, load amsmath and use an environment that accepts a double backslash: multline for one long equation, split inside equation for aligned lines under one number, or align for several aligned equations. A double backslash inside a plain equation environment is ignored, so the formula stays on one line.