Replace Lagrange multiplier method

This book is primarily written for students majoring in science and engineering, teachers in science and engineering, engineers, technicians, middle school teachers and philomaths. The philosophy of "Mathematics around us" is proposed, and the idea of correspondence is considered as a tool to deal with complex and profound questions. By interpretations for multivariate function, an error which exists in test books of mathematics for more than 100 years is corrected. After new approaches to solving extremum are developed, Language multiplier method that is widely applied in mathematics, physics, engineering and technology will have fulfilled its historical task. Using n-dimensional outer product, the dispute (if multiplier is unique or not) will end. Helping this new methods, we can calculate distance among point, curves, surfaces.