Question 1060419
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Simplify:

{{{sqrt( (sqrt(21)-2sqrt(7))^2)}}}
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<pre>
{{{sqrt( (sqrt(21)-2sqrt(7))^2)}}}  has TWO values.


One value is  {{{sqrt(21)-2sqrt(7)}}}.


Another value is  {{{-(sqrt(21)-2sqrt(7))}}} = {{{2sqrt(7) - sqrt(21)}}}.


Same  as  {{{sqrt(a^2)}}}  has two values.  One is  |a|.  Another is  -|a|.
For any real a =/= 0.


If a = 0, then  {{{sqrt(0)}}} = 0  has only one value.
</pre>

Calculations that "josgarithmetic" does in his response, are absolutely unnecessary.
They do not lead to the simplest form.
In opposite, they require to be simplified further.


So, writing by "josgaritmetic" is totally out of the goal of this assignment.