help solving this please

15. Use implicit differentiation to find dy/dx. x'y + = 4 16. Find the equation of the tangent line to the curve y = f(x) at the given x-value and indicate the solution. f(x) = xe- at x=1 a. y = 2x -1 b. y = 5x - 4 C. Y = -2x +3 d. y = 3x-2 17. Find the linear approximation for the square root of 50 by using the square root function and the fact that the square root of 49 is 7. Make use of : f ( x + V x) = f (x) + f (x) dx