Posted by student on Monday, February 13, 2012 at 9:59pm.
Find the interval (or intervals) on which the given expression is defined:
(x^27x+12)^(1/2)

algebra  Reiny, Monday, February 13, 2012 at 10:04pm
we can write it as
√[(x3)(x4) ]
remember that we cannot take √ of a negative number
the critical values above are x=3 and x=4
for values between 3 and 4, the result is negative,
e.g. x = 3.5 , we get √(.5(.5)) = √.25 which is undefined.
so we need
x ≤ 3 OR x ≥ 4

algebra  student, Monday, February 13, 2012 at 10:10pm
Wouldn't they both be > or = to?

algebra  Reiny, Monday, February 13, 2012 at 10:17pm
no, take an example of x ≤ 3
e.g. x = 5
expression is
√(8)(9) = √72 which is a real number
Trust me, my answer is correct.

algebra  student, Monday, February 13, 2012 at 10:38pm
Yes you're right. THANK YOU SO MUCH!!
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