Solving Noether's Theorem: Examining "Reverse" Transformation

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Hello, I've reading "Emmy Noether's wanderfull therorem" by Neuenschwander and he asks this question as exersice:
We described a transformation that takes us from (t, x) to (t', x') with
generators ζ and τ . How would one write the reverse transformation from (t', x')
to (t, x) in terms of the original ζ and τ? If the functional is invariant under the
‘forward” transformation, is it also invariant under the “reverse” transformation?

I would like to Know whether my answer is correct.
For the first question I found that for the inverse tansformation ζ and τ change signs, as for the second question I found that the invariance stands using either the "forward" or "reverse" transformation.
 
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Your statements are correct, they are connected to the group theory structure of symmetries of the Lagrangian.
 
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