Find an equation of the tangent plane to the given surface at the specified point. 3. z = 2x² + y² - 5y, (1, 2,-4) 4. z = (x + 2)² - 2(y - 1)² - 5, (2,3,3) 5. z = e, (2, 2, 1) 6. z = y²e¹,