First of all we would break 256 into its simple factors.
2 / 256
2 / 128
2 / 64
2 / 32
2 / 16
2 / 8
2 / 4
2 / 2
1.
Therefore 256 = 2 * 2 * 2 * 2 *2 * 2 * 2 *2
Therefore sixth root of 256 =
![\sqrt[6]{2*2*2*2*2*2*2*2}](https://img.qammunity.org/2015/formulas/mathematics/high-school/v4aijvqmdpysretm4jn26v9khuf30b7tgf.png)
For every six 2s we bring out one out of the root.
=
![2\sqrt[6]{2*2}](https://img.qammunity.org/2015/formulas/mathematics/high-school/joz760c87g0zj2vaasgk4j8vf946pk57p7.png)
=
![2\sqrt[6]{4}](https://img.qammunity.org/2015/formulas/mathematics/high-school/8fz21wsvi98rbt1pi41qoqdvzndndtt6fu.png)
That's our answer.