URL：https://media.cheggcdn.com/media/fe0/fe007732-fe50-4dcd-ae6f-b693e00c698a/phpKWPeT8
掲載元：https://www.chegg.com/homework-help/questions-and-answers/let-x-~-n-0-1--define-density-function-random-variable-y-x2-b-let-also-y-~-n-0-1-define-de-q91573932
