1) a) (Ex. 1.5.2 (c), 2pts) For vectors x, y E R" show the polarization identity 4 = |/x + yl/2 - |/x -yl/2 b) (Review exercise 1.20, 2pts) Show that the vectors |ly| |x + | |x|ly and |ly| |x - | |xlly are orthogonal. c) (Review exercise 1.26, 4pts) Show that two planes given by the equations Ax + By + Cz+ D1 = 0 and Ax + By + Cz + D2 = 0 are parallel, and that the distance between them is (D1 - D21 VA2 + B2 + C'2