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I have flashcards that work perfectly, but on a few of my flashcards I want to be able to give 2 equations on separate lines. Normally I know how to do this....such as using gather or align but when I try to use this, I'm getting errors that I don't understand. Below is my attempt, thanks for the help! (the flashcard package is something I downloaded, but I don't think it should matter)





\begin{flashcard}[]{Lorentz transformation for motion along x (for t' and x')}
t' = \gamma \left(t - \frac{vx}{c^2} \\
x' = ....


Of course this gives the error "! Package amsmath Error: Erroneous nesting of equation structures; (amsmath) trying to recover with `aligned'."

marked as duplicate by Werner, Fran, mafp, Martin Schröder, Red Sep 19 '13 at 21:01

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