Question: 1. Use the change of coordinates x = 2s + t, y = s - t to compute the integral R(x+y) dA, where R is the parallelogram formed by (0, 0), (3, -3), (5, -2), and (2, 1).
2. Use the change of coordinates s = x + y, t = y to find the area of the ellipse x2 + 2xy + 2y2 ≤ 1.