D[((x*l1 + (1 - x)*l2)/(x^2*v1 + (1 - x)^2*v2 + 2*x*(1 - x)*c)^0.5)+((x*L1 + (1 - x)*L2)/(x^2*V1 + (1 - x)^2*V2 + 2*x*(1 - x)*C)^0.5), x]

Gives me the first derivative. I want to set it to zero, and solve for x. How does one do that in Mathematica?

Thanks in advance.

Alonso