# If I have a production function f where the marginal product of all the input is constant, can f exhibit decreasing returns to scale? [duplicate]

Marginal product of input xi= $$$$\frac{\partial f }{\partial x _{i}}$$$$

Yes: $$f(x_1,x_2)=-x_1x_2$$ has constant marginal return in both inputs and decreasing return to scale by your definition.