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اثبات

(1)   study  = don't fail

(2)  don't study = fail

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(1) + (2)  ----->   study + don't study  = fail + don' fail  .   ok ?

study ( 1+don't) = fail ( 1+ don't )       ok ?

study ( 1+don't) = fail ( 1+ don't ) 

study  =   fail   !   

so  , don't study