Please help me understand! THANKS so much

3. + -/2 points Which of the following matrices is a projection matrix? Select all that apply. 7 4. + -/2 points Let A be a matrix with full rank (that is a matrix with a pivot position in every column). Which of the following statements are always true: [Select all that apply] A least squares solution to the equation Ax = b is equal to zero if and only if be Nul (A). n x such that |Ax - b| is minimal. n the orthogonal projection of b onto Col (A). n equal to the solution of the equation Ax = b if and only if be Col (A). n equal to zero if and only if be Nul (AT ).5. +-/2 points You wish to find the parabola of best fit for the data points (1, -1). (-3, 1), (2, 2) and (-1, 1). Given that a least squares solution for the system X = 81 is x = 1 398 77 , which of the following is the parabola of best fit? 14 81 17 14 81 2 + 398 - 14 398 None of the other answers O V= 14 + 81 398 308 + 77 308 O V= 14 2 + 398 81 308 + 77 3981. o 12 points 1 0 Let {31132133134135} be an orthogonal basis for R5 with :13 = 1 , let 0 1 1 L11 .7: = 1 , and let W = span{u11u21u41u5}. Whidl one of the following 1 1 equals my, the orthogonal projection of .7: onto W? 1 0 17W = 1 0 m 1 0 1 17W = 0 1 0 1 0 0 .n. 1 0 1 1 .n. 0 1 1 17W 1 1 m 1 1 1 1