x² + y² and 5. Evaluate the limit using the substitution z = observing that z →0+ if and only if (x, y)⇒(0, 0). e-1/√√x²+y2 12. lim (x,y)→ (0,0) √x² + y² Solution: 1 1 พ 12. With 2 = x² + y², lim -1/√; let w = lim = 0. 2-0