Help with Multi Variable Calculus

3. If f(x, y) = x2 + 74. does lim f(x, y) exist? (z,y) (0,0) 4. Let z = In(c* + cy). Find oz and oz + ay + 82 2 dedy 5. The temperature at a point (x. y) on a flat metal plate is given by 60 T(x, y) = 1 + x2 4 12 : Where T is measured in "C and x, y in meters. (a) Find the rate of change of temperature with respect to distance at the point (2, 1) in the x-direction. (b) Find the rate of change of temperature with respect to distance at the point (2, 1) in the y-direction