i have a couple questions where im stuck at the part where i have to solve for x. these are the equations in which i need to solve for x

15x/(x^2 +14400)^(1/2) -10 = 0

and

4c(2x^2)+c(2x^2)+c(2880/x)+c(1440/x)

where i need to first solve for the derivative and then solve for x