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The following code:

            \begin{align*}
                2(3-x) \leq 2 &\Leftrightarrow 6-2x &\leq 2 \\ 
                              & \Leftrightarrow -2x &\leq 2-6  
            \end{align*}

looks like this

enter image description here

does not align \leq, how one can align in this example the \leq signs? Thnak you!

Zarko
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user91328
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    the & in align treat the intervening material in pairs, with each pair being handled as an independent equation, "centered" on the sign of relation. so to get the right-hand expressions to line up "to the left", insert two & before them. (i'll look for a duplicate; i know this has been answered before.) welcome to tex.sx. – barbara beeton Nov 03 '15 at 17:05
  • @barbarabeeton, as you say, above question is probably duplicate, but anyway, help to beginner on SE list and convert your comment to answer. – Zarko Nov 03 '15 at 17:08
  • the answer to this question explains the alignment protocol when multiple elements appear on a single line of an aligned display: Difference between align and alignat environments. – barbara beeton Nov 03 '15 at 17:19
  • @Zarko -- done. (i wanted to steal some of the text from the answer i knew existed; it's described much better than what i wrote in the first comment.) – barbara beeton Nov 03 '15 at 17:28

1 Answers1

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the align environment is based on pairs of rl columns; it will create as many as desired based on the environment's contents, and add horizontal space between the column pairs:

<r col><l col> <space> <r col><l col> <space> <...>

the segments on a line are separated by &, so if a column is omitted, the & must still be present to keep the proper alignment for the remaining columns.

barbara beeton
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