Write the sum in sigma notation. $ \noindent 1 - x + x^2 - x^3 + \cdot\cdot\cdot + {(-1)}^n x^n $

Select the correct answer from each drop-down menu. a system of equations and its solution are given below. system a complete the sentences to explain what steps were followed to obtain the system of equations below. system b to get system b, the equation in system a was replaced by the sum of that equation and times the equation. the solution to system b the same as the solution to system a.]