[Tex/LaTex] Align left-aligned formula at two points

Question

I would like to get this WITHOUT using tables, because in my real equations there are fractions included that are scaled down in tables

a+b+c=1
y    =2

My code looks as follows:

\begin{align*}
&a+b+c&=1\\
&y    &=2
\end{align*}

But it doesn't work. I tried thousands of things such as flalign and so on. But nothing works. I am really frustrated. Any ideas?

Answer 1

You can use "big fractions" also inside array; using the array package helps, so say

\usepackage{array}

in your preamble. Then you can use

\begin{array}{@{}>{\displaystyle}l@{}>{\displaystyle{}}l@{}}
a+b+c &= y           \\
y     &= \frac{2}{3}
\end{array}

just as a single (math) object that you can put anywhere you like. Adding \vphantom{\frac{2}{3}} before the \\ in the first row can help spacing.

For example, with

\begin{flalign*}
\begin{array}{@{}>{\displaystyle}l@{}>{\displaystyle{}}l@{}}
    a+b+c &= y           \vphantom{\frac{2}{3}}\\
    y     &= \frac{2}{3}
\end{array}
&&
\end{flalign*}

you'll get the object flush with the left margin.