Question 74599
Find the domain of f(x) = 7+(square root sign) 3x +21 and express it using interval notation. 
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y = 7 + sqrt(3x+21)
That 3x+21 must not be negative; it must be greater than or equal to zero
so that y can be a Real numberl
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So, 3x+21>=0
3x>=-21
x>=-7
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So, Domain is all Real numbers x>=-7
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Cheers,
Stan H.