这本论及高等数学的难题。
到他14岁的时候，他已经自学了高等数学，这也是他能够解答这道难题的原因。
By the time he was 14, he had studied advanced math on his own. It was the reason that he could answer the difficult math problem.
到他14岁的时候，他已经自学了高等数学，这也是他能够解答这道难题的原因。
By the time he was 14, he had studied advanced math on his own. It was the reason that he could answer the difficult math problem.
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