Question 145955
Find the domain (the interval(s) on the real number line for which the radicand is nonnegative, greater than or equal to zero). 
Square root x-3 
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x-3 must be greater than or equal to zero
x-3>= 0
x >= 3
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Draw a number line and mark a point x = 3
Make a black circle at that point.
Draw a ray (arrow) to the right from that point.
That is the figure you want.
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Cheers,
Stan H.