of where f(x, y) = xtacyty: Use the formal definition of the partial derivative to find ax of f(x th, y) - f(x, y) -lim lim ax h-0 h h-0 of Evaluate at (1, 3): axUse the table below to approximate fx(3, 4). 2 3 4 5 X -6 -4 -2 0 2 2 -11 -9 -7 -5 -3 3 -16 1-14 -12 -10 -8 4 -21 -19 1-17 1 -15 -13 5 -26 -24 -22 -20 18 fx(3, 4) =