(Requires Calculus)For the Case of the Multiple Regression Problem with Two

Essay

(Requires Calculus)For the case of the multiple regression problem with two explanatory variables, show that minimizing the sum of squared residuals results in three conditions: $$\sum _ { i = 1 } ^ { n } { \hat u_ { i } } = 0 ; \sum _ { i = 1 } ^ { n } \hat { u _ { i } } X _ { 1 i } = 0 ; \sum _ { i = 1 } ^ { n } \hat { u _ { i } } X _ { 2 i } = 0$$