Align equation

[slender widget]

Good evening
I can't align and center an equation, can someone help me ?
Code

\begin{bclogo}[ couleur= lightgoldenrodyellow , arrondi = 0.1 , logo =  \bclampe ,  barre =
zigzag]{ Solution n°2}
The concatenation of languages $L_1$ and $L_2$ is defined as
\[L_1L_2 = \{ xy \phantom{a}|\phantom{a} x \in L_1, y \in L_2 \} \]
The reverse of a language L is defined as  \[L^R :=
 \{x^R \phantom{a}|\phantom{a} x \in L \}\] 
\[ (L_1L_2)^R = \{ xy \phantom{a}|\phantom{a} x \in L_1, y \in L_2 \}^R = \{ (xy)^R \phantom{a}|\phantom{a} x \in L_1, y \in L_2 \}  \] 
\[ =\{ y^Rx^R \phantom{a}|\phantom{a} x \in L_1, y \in L_2 \}^R = \{ yx \phantom{a}|\phantom{a} x \in L_1^R, y \in L_2^R\} \] 
\end{bclogo}

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Valentinn
Compile Error! Click the reaction for more information.
(You may edit your message to recompile.)

[thick hemlock]

Are you talking about the second equation block? If so, I'm guessing what you meant by aligning them,

\begin{gather*}
L^R := \{ x^R \phantom{a}|\phantom{a} x \in L \}
\\
\begin{aligned}
(L_1L_2)^R &= \{ xy \phantom{a}|\phantom{a} x \in L_1, y \in L_2 \}^R = \{ (xy)^R \phantom{a}|\phantom{a} x \in L_1, y \in L_2 \}
\\ 
&= \{ y^Rx^R \phantom{a}|\phantom{a} x \in L_1, y \in L_2 \}^R = \{ yx \phantom{a}|\phantom{a} x \in L_1^R, y \in L_2^R\}
\end{aligned}
\end{gather*}

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lstenger

[slender widget]

Thanks!!

I tried aligned alone but it wasnt working