<PRE><B>Question 234338</B>
I am supposed to solve: 
sqrt with the radicand 5x +21, then = x+3. So the question is: 
sqrt(5x+21) = x+3
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Square both sides to get:
5x+21 = x^2 + 6x + 9
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Then x^2 + x - 12 = 0
(x+4)(x-3) = 0
x = -4 or x = 3
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Since you squared, you have to check for extraneous answers.
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Checking x = -4 you get:
sqrt(-20+21) = -4+3
sqrt(1) = -1
1 = -1 
False ; so x = -4 is extraneous
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Checking x = 3 you get:
sqrt(15+21) = 3+3
sqrt(36) = 6
6 = 6
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Final Answer: x = 3
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Cheers,
Stan H.</PRE>