How do you find the cube roots #root3(729)#?

1 Answer
Nov 29, 2016

#root(3)729=9#

Explanation:

Let us first factorize #729# in to rime factors. As sum of digits of #729# is #18#, it is divisible by #9# i.e. we can divide it twice by #3#. Therefore

#729=3xx3xx81#

Again #81# is #9^2#, hence divisible bt #3# four times more. Hence,

#729=3xx3xx3xx3xx3xx3xx3#

and #root(3)729=root(3)(ul(3xx3xx3)xxul(3xx3xx3))#

= #3xx3=9#