Question 1006922
<pre>
That's a square root not a fourth root.

{{{ sqrt( 81x^4y^16z^28 ) }}}

The square root is the 2nd root, so write in the understood index, 2.

{{{ root(2, 81x^4y^16z^28 ) }}}

Write 81 as 9<sup>2</sup>

{{{ root(2, 9^2x^4y^16z^28 ) }}}

Divide the index 2 into each exponent and
that removes the square root since 2 will go into
each exponent evenly, without leaving any remainder.

{{{9^1x^2y^8z^14}}}

{{{9x^2y^8z^14}}}


Edwin</pre>