Question 159415
The domain is the values of x where the function makes sense.
For square root functions to make sense, the argument must be greater or equal to 0.
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{{{f(x)=sqrt(8-sqrt(8-x))}}} 
First off,
{{{8-x>=0}}}
{{{x<=8}}}
The upper bound for x is 8.
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The second argument must also be greater than or equal to 0.
{{{8-sqrt(8-x)>=0}}}
{{{sqrt(8-x)<=8}}}
{{{(8-x)<=64}}}
{{{-x<=56}}}
{{{x>=-56}}}
The domain for x is [56,8]