1) Determine the basis for subspace of all vectors (x1; x2; x3; x4) in R4 such that x1 + x2 = x3 + x4.
2) Assume that x0 is solution to equation Ax = b (where A is matrix and x and b are vectors). Illustrate that x is solution to Ax = b if and only if y = x - x0 is solution to system Ay = 0.