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Problem #18: Which of the following sets are closed under scalar multiplication? [2 marks] (i) The set of all vectors (a, b) in R2 such that 6a + 46 = 5. (m) The set of all polynomials ax + bx + c in P2 such that b2 - 4ac = 0 (iin) The set of all 2 x 2 matrices that commute with the matrix|$ ; (A) (ii) only (B) (1) and (mii) only (C) none of them (D) all of them (E) () and (ii) only (F) (ii) and (iii) only (G) (in1) only (H) (1) only Problem #18: Select v] Save | Your work has been saved!_/Back to Admin Pagel Problem #19: Given [2 marks] 21 = -25 -51, and z2 = 1-51. let z = 2172 - 3. Find |z). Problem #19: Save | Your work has been saved! [Back to Admin Bagel Problem #20: Which of the following statements about complex numbers are always true? [2 marks] (@) Let 21 = rell and zy = peltz. Ifz1 = zz then 61 = 02. (ii) If z = rel then (2] = P. (im) There is only one complex number z that satisfies the equation ?= (A) (1) and (ii) only (B) all of them (C) (ii) and (mii) only (D) none of them (E) (1) only (F) (1) and (ini) only (G) (i1) only (H) (1) only Problem # 20: [Select v ] Save | Your work has been saved! (Back to Admin Page) Problem #21: Consider the matrix [2 marks] [4476 0 0 4476 1476 4476 The matrix , has A = 4476 as an eigenvalue. What is the geometric multiplicity of 1 = 4476? Problem - 21