Centering Equations

centering_equations

---
title: "centering equations"
output:
  pdf_document: default
classoption: fleqn
header-includes: 
 - \setlength{\mathindent}{0pt}
 - \setlength{\parindent}{0pt}
---

This is some text

This is the equation I would like left aligned:
\[
  h(t_{ij}) = Pr[ T_i = j| T_i \geq j |
\]

This is the equation I would like centred:
\[
  \makebox[\linewidth]{$h(t_{ij}) = Pr[ T_i = j| T_i \geq j |$}
\]

\noindent
\makebox[\linewidth]{centered text}

This is a set of equations to align centred:
\[
  \makebox[\linewidth]{$\displaystyle
    \begin{aligned}
               f(x) &= ax^2 + bx + c \\
      ax^2 + bx + c &= g(x)
    \end{aligned}
  $}
\]



From: https://tex.stackexchange.com/a/390656