数学的力量在于它简化复杂事物的能力。

There are two ways to extend a business. Take inventory of what you are good at and extend out from your skills. Or determine what your customers need and work backwards, even if it requires learning new skills.

——1912年在旧金山丽蝉戏院的演说

记忆是个骗子，总是在重写过去。