=7/3
∂f/∂x=2xy+ye^xy→fx(1,2)=4+2·e²
dz=∂z/∂x·dx+∂z/∂y·dy=(y+1/y)dx+(x-x/y²)dy
∂z/∂x=1/(x-2y)→∂²z/∂x∂y=-[-2/(x-2y)²]=2/(x-2y)²
∂z/∂x=2xy+ye^xy ∂z/∂y=x²+xe^xy
dz|(1,0)=2dy
