Michael J. answered • 03/28/15
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Effective High School STEM Tutor & CUNY Math Peer Leader
f(v) = √(-3x + 21)
The number under the square-root cannot be negative, since there is no number when squared will result in a negative value.
-3x + 21 ≥ 0
-3x ≥ -21
x ≥ 7
Flip the inequality sign when dividing by a negative number.
x ≤ 7
The domain is (∞, 7].
