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# Finding the domain of a function?

Say you were finding the domain of a function with a square root in the denominator. You would set it >=0 correct? but since you look at the denominator to find the domain of a function cant we just make it >0? im confused as to why we use >=0

### 2 Answers

- TomVLv 71 month ago
If the square root is in the denominator of a rational function, the value of the expression under the radical must be greater than zero for the function to be defined and real valued. In that case, you would not use ≥ 0 because if it were 0, the function would be undefined because of division by zero.

If the square root is not in the denominator, than you can use ≥ 0 because a zero value for the square root would not be a division by zero.

So, it depends on whether the square root is in the numerator, in which case the radicand must be ≥ 0, or in the denominator in which case the radicand cannot be zero but must be > 0.

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- D gLv 71 month ago
generally a root has to have a positive numbber inside the sqrt sign

if on the bottom of a fraction the number cannot be zero

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