Please note the two parts in this question are not related. [a] Find an equation of the tangent plane to the surface of a = Byeirwyajat (1: _2: _6)' [bi Given that the function a = at, y) is a differentiable function with f(1,3) = 4, fz(1, 3) = 1, fy(1, 3) = 2. find the linear approximation and the differential of the function at {1,3}. Use the differential to estimate the total change a: when x is increased by 0.03, and v is decreased by 0.02. Enter your answer in the blank below. Round your answer to two decimal places. Your Answer: [