Object moving in the xy-plane is acted on by a conservative force described by the potential-energy function u(x, y)=α(1/x2+1/y2), where α is a positive constant

It seems like the problem is asking for us to derive an expression for the force F⃗ stated in terms of the unit vectors i^ and j^.

The solution for this is:

U(x,y) = α (x^-2 + y^-2) 

F = - dU(x,y) 

F = - (dU/dx + dU/dy) 

F = - (-2αx^-3 - 2αy^-3) 

F = 2α (x^-3 + y^-3)

F = 2α (1/x^3 i + 1/y^3 j) 

the answer is 13 cm

he has 140 chickens because he has 10 times more chickens than ducks and he has 14 ducks so 14*10=140