1. Explain what it intuitively means for function f(x, y) to be continuous in some domain D. 2. Consider the function below and the point (1r,y,z) shaded in red. ls f3 positive, negative, or zero? What about fy? Z 3. (True/False) [f f(:1:,y) has a local minimum and is differentiable at (a,b), then f(a,b) = U for any unit vector 11'. 4. (True/False) Two lines in three-diniensional space either intersect or are parallel. 5. (True/False) Every.r critical point is either a local maximum or a local minimum. 6. (True/False) Two lines in two-dimensional space either intersect or are parallel. 7. (True/False) For any three-dimensional vectors 21' and if, we have |11' X 5| = |fF X |. 8. (True/False) Two lines in three-diniensional space parallel to a plane are parallel to one another. 9. (True/False) If f(:r,y) is a continuous function on a closed, but unbounded set D, then f(:s,y) cannot achieve a local maximum on D. 10. (True/False) For any continuous function f(:.c, y), we have fzy = fyg