Equation
Prove that for any $c\in (0,1)$ the equation $$\left(1-\left(c-cx\right)^{2/3}\right)^3=(1-c^2)x^2$$ has unique real root in $(0,1)$ and find this root. Comment. This Problem has connection with a property of the astroid - being the curve which is obtained as a contour of the set of lines ending at the two axes and with unit length.