a. Find the linear approximation for the following function at the given point. b. Use part (a) to estimate the given function value. f(x,y) = 3x - 7y +9xy; (4,5); estimate f(4.1,5.02) a. L(x,y) = b. L(4.1,5.02) = (Type an integer or a decimal.) a. Find the linear approximation for the following function at the given point. b. Use part (a) to estimate the given function value. f(x,y) = 1x2 + y2 ; (12, -5); estimate f(12.07, - 4.94) a. L(x,y) = b. L(12.07, - 4.94) = (Type an integer or decimal rounded to three decimal places as needed.) Use differentials to approximate the change in z for the given change in the indeper variables z=x - 3xy + y when (x,y) changes from (4,4) to (4.03,3 95) dz = (Type an integer or a decimal.) 8. Use differentials to approximate the change in z for the given change in the independent variables z = In (x y) when (x,y) changes from ( - 2,5) to ( - 1.99,4.99) dz = (Type an integer or a decimal.)