A proof is a device for convincing someone else that a mathematical statement is true.
证明是一种用于使他人相信数学陈述为真的工具。
如果拜登当选，你将要付7元、8元、9元。
The secret of joy in work is contained in one word – excellence. To know how to do something well is to enjoy it.
We are constantly refining our models to improve performance.
Sometimes the most unexpected findings lead to the greatest advances.