Schau mal ob das so richtig ist.
Fx'(x, y) = 231·y^{21/100}/(25·x^{17/50})
Fy'(x, y) = 147·x^{33/50}/(50·y^{79/100})
y'(x, y) = - Fx'(x, y) / Fy'(x, y) = - (231·y^{21/100}/(25·x^{17/50})) / (147·x^{33/50}/(50·y^{79/100}))
y'(x, y) = - 22·y/(7·x)
y'(2, 3) = - 22·3/(7·2) = -4.714285714