\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage[]{amsthm} %lets us use \begin{proof}
\usepackage[]{amssymb} %gives us the character \varnothing
\usepackage[fleqn]{amsmath}
\usepackage{amsfonts}
\begin{document}
\maketitle
\begin{enumerate}
\item $\sum_{i = 4}^{n} (4i^2+2i)$
\begin{flalign*}
\begin{split}
&= \sum_{i = 4}^{n}4i^2+\sum_{i = 4}^{n}2i
\\
&= 4\sum_{i = 4}^{n}i^2+2\sum_{i = 4}^{n}i
\\
&= 4(\sum_{i = 0}^{n}i^2-\sum_{i = 0}^{4-1}i^2)+2(\sum_{i = 0}^{n}i-\sum_{i = 0}^{4-1}i)
\\
&= 4(\sum_{i = 0}^{n}i^2-\sum_{i = 0}^{3}i^2)+2(\sum_{i = 0}^{n}i-\sum_{i = 0}^{3}i)
\\
&= 4(\sum_{i = 0}^{n}i^2-0^2-1^2-2^2-3^2)+ 2(\sum_{i = 0}^{n}i-0-1-2-3)
\\
&= 4(\sum_{i = 0}^{n}i^2-0-1-4-9)+ 2(\sum_{i = 0}^{n}i-0-1-2-3)
\\
&= 4(\sum_{i = 0}^{n}i^2-14)+ 2(\sum_{i = 0}^{n}i-6)
\\
&= 4(\sum_{i = 0}^{n}i^2-14)+ 2(\sum_{i = 0}^{n}i-6)
\\
&= 4(\sum_{i = 0}^{n}i^2-14)+ 2(\sum_{i = 0}^{n}i-6)
\end{split}
\end{flalign*}
\item
\end{enumerate}
\end{document}
答案1
像这样?
\documentclass{article}
%\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage[fleqn]{amsmath}
\usepackage{amssymb} %gives us the character \varnothing
\usepackage{amsthm} %lets us use \begin{proof}
\begin{document}
\begin{enumerate}
\item $\begin{aligned}[t]
\sum_{i = 4}^{n} (4i^2+2i)
&= \sum_{i = 4}^{n}4i^2+\sum_{i = 4}^{n}2i \\
&= 4\sum_{i = 4}^{n}i^2+2\sum_{i = 4}^{n}i \\
&= 4\biggl(\sum_{i = 0}^{n}i^2-\sum_{i = 0}^{4-1}i^2\biggr)+2\biggl(\sum_{i = 0}^{n}i-\sum_{i = 0}^{4-1}i\biggr) \\
&= 4\biggl(\sum_{i = 0}^{n}i^2-\sum_{i = 0}^{3}i^2\biggr)+2\biggl(\sum_{i = 0}^{n}i-\sum_{i = 0}^{3}i\biggr) \\
&= 4\biggl(\sum_{i = 0}^{n}i^2-0^2-1^2-2^2-3^2\biggr)+ 2\biggl(\sum_{i = 0}^{n}i-0-1-2-3\biggr) \\
&= 4\biggl(\sum_{i = 0}^{n}i^2-0-1-4-9\biggr)+ 2\biggl(\sum_{i = 0}^{n}i-0-1-2-3\biggr) \\
&= 4\biggl(\sum_{i = 0}^{n}i^2-14\biggr)+ 2\biggl(\sum_{i = 0}^{n}i-6\biggr) \\
&= 4\biggl(\sum_{i = 0}^{n}i^2-14\biggr)+ 2\biggl(\sum_{i = 0}^{n}i-6\biggr) \\
&= 4\biggl(\sum_{i = 0}^{n}i^2-14\biggr)+ 2\biggl(\sum_{i = 0}^{n}i-6\biggr)
\end{aligned}$
\item
\end{enumerate}
\end{document}
如您所见,方程式是内联模式。对于多行环境使用aligned
环境。