Packages and Common Math Environments

Loading a package

\usepackage{amsmath}

amsmath (loaded in the preamble, before \begin{document}) unlocks the environments below and is close to mandatory for any STEM document.

Aligning multi-line equations

\begin{align}
  y &= (x+1)^2 \\
    &= x^2 + 2x + 1
\end{align}

The & marks the alignment point (usually right before the =), so every line lines up vertically — exactly what a worked derivation needs.

A matrix

\begin{pmatrix}
  1 & 2 \\
  3 & 4
\end{pmatrix}

Why This Matters for Your Exams

align is what makes a multi-step derivation readable instead of a wall of separate equations — it's the single most useful environment for a mathematics write-up.