1/ $\sqrt[3]{{16}} - \sqrt[3]{{2x + 1}} = \sqrt[3]{{2x - 1}}$
2/ $\sqrt[4]{{x + 1}} + \sqrt x = 1 + \sqrt[4]{{{x^3} + {x^2}}}$
3/ $\sqrt {{x^2} + x + 6} + \sqrt {{x^2} + x + 2} = x + \frac{4}{x}$
4/ $x\sqrt {1 + \frac{1}{x}} + \frac{1}{x}\sqrt {x + 2} = 1 + \sqrt {x + \frac{2}{x} + 3} $