4. (a) Find the leastsquares approximation to the solution of the system of equations: 2x+y=1 xy=1 x+y=2 (b) Let S be the plane passing through the origin 0 and the points U = (2, 1, 1) and V = (1, l, 1). Use your answer to (a) to nd the foot F of the perpendicular dropped from W = (l, l , 2) to S. (0) Check your solution by verifying that the error vector 3 = FW is orthogonal to u and v. 5. Find equations for all the planes that intersect the yaxis at y = l and the zaxis at z = 2, and are tan gent to the sphere (x 2)2 + y2 + 2'2 = 4. Do not use calculus