Square Root
If $x^{2} = y$, we say that the square root of y is x and we write, $\sqrt{y}=x$
Cube Root
The cube root of a given number x is the number whose cube is x. we denote the cube root of x = $\sqrt[3]{x}$
e.g. $\sqrt[3]{27} = \sqrt[3]{3\times3\times3} = 3$
Note:
1)$\sqrt{xy}=\sqrt{x}\times\sqrt{y}$
2)$\sqrt{\frac{x}{y}}=\frac{\sqrt{x}}{\sqrt{y}}=\frac{\sqrt{x}}{\sqrt{y}}\times\frac{\sqrt{y}}{\sqrt{y}}=\frac{\sqrt{xy}}{y}$