(15) Let a, b = Z. Prove that if a is divisible by 4 and b is divisible by 4, then: (a) ab is divisble by 16. (b) a - b is divisible by 4. (c) Is the converse of either part true or false? Justify your answer.

|a+2b] 2 O Let W = - b :a,be R}. Show that -4 lies in W+. 2a -1

Service Sy. Find, if possible, A+ B, A- B, 2A, 2A - B, and 8+ A. (If not possible, enter IMPOSSIBLE in any single cell.) 国 213 A = 250 -14 2 0 2 (a) A+B (b) A-B (c) 2A (d) 24 - B P Type here to search 立 00

Perform the indicated operations ,expressing all answers in the form a+bj 5) (3-7j)+(2-j) 6)(-4-j)+(-7-4j) 7)(7j-6)-(19-3j) 8)(5.4-3.4j)-(2.9j+5.5) 9)0.23-(0.46-0.19j)+0.67j

4. Express in terms of i (a) 3-I (b) V-4 (c) V-36