Please explain why in each case

Question3 Which of the following is a reason why LU decomposition is useful in application? Note: In the following, "cheaper" refers to a lower order-of-operation count. O It is cheaper than Gaussian elimination O It is cheaper than Gaussian elimination when solving systems Ax-b repeatedly for different A'matri It is cheaper than Gaussian elimination when solving systems Axeb repeatedly for different b' vecto O The algorithm can be used to solve systems with singular matrices Question 4 Suppose A is a matrix in MATLAB and I run the following code: Which of the following is guaranteed to be true? O A is (approximately) equal to LU*P PA is (approximately) equal to l'U O A is (approximately) equal to P.L-U A is (approximately) equal to L'Uu Question 5 vat to ue Al t a coda [L,U,P]-lu(A); Which of the following lines of code will solve for x? y LP*b)