Answer Happy

Please answer the questions of 1&9 in 6.2.
Exercises 6.2 1. Solve the following system by Gaussian elimination. x1 + x2 + x3 = 2 2x1 + x2 + x3 = 3 x1 - x2 + 3x3 = 8 9. A system Ax = b of n linear equations in n unknowns has a unique solution if and only if det A +0. Is it a good idea to check this condition before applying Gaussian elimination to a system?