Joseph Louis-Lagrange (1736-1813)

Joseph Louis-Lagrange was born into a wealthy family. His father served as a fiscal counsel to the king of Sardinia, but lost the family fortune in a series of faulty investments. Lagrange later claimed that if he had been rich, he would have most certainly idled his life away, but because he was poor, by necessity he was forced to acquire an education. His fiscal situation kept him out of private schools, and most of his basic education came from books of his own choosing. His earliest papers were concerned with topics in applied physics, specifically astronomy and optics theory. His talent for mathematics was discovered at an early age. By age 19, he had his first teaching job. He extended differential equations into the areas of fluid mechanics. Towards this end, he developed the method of variation of parameters for solving certain classes of ordinary partial derivatives. He also made contributions in the field of probability. He is responsible for the first known proof of the four-squares property, which states that every positive integer can be expressed as the sum of four squares. Towards the end of his life, Lagrange was inducted into the Legion of Honor by Napoleon.