# Math Help - Square root of a negative number that is squared

1. ## Square root of a negative number that is squared

The value of square root of (√(-9)^2) is:

-9
9i
3
9
none of these

which one is the right answer?

2. i would say the ^2 and the √ cancel each other out leaving -9. But as with every reply i post, im not confident lol

I just typed it into the calc and it reads 9. So basically, im useless lol

3. Originally Posted by alaricepent
The value of square root of (√(-9)^2) is:

-9
9i
3
9
none of these

which one is the right answer?
So this is what I see:

(√(-9)^2)

The square root is over the everything, right? Something like sqrt( (-9)^2)? If so:

The answer is 9. First you square (-9), then you will have sqrt( 81), which is just 9.

However, just to clarify, if you have:

[ √(-9) ]^2, then the answer is just -9 because the square and square root cancels out. I hope that helps.

4. Originally Posted by alaricepent
The value of square root of (√(-9)^2) is:

-9
9i
3
9
none of these

which one is the right answer?

$= {\sqrt {(-9)^2}}$

$= {\sqrt {81}}$

$={9}$

5. Originally Posted by alaricepent
The value of square root of (√(-9)^2) is:

-9
9i
3
9
none of these

which one is the right answer?
(-9)(-9) = 81 since a negative times a negative equals a positive.
square root(81) technically = -9 and 9, but sinc ethis is in elementary and middle school math section, I'm assuming you're only dealing with positive numbers. So, the answer would be 9

6. Originally Posted by kathrynmath
(-9)(-9) = 81 since a negative times a negative equals a positive.
square root(81) technically = -9 and 9, but sinc ethis is in elementary and middle school math section, I'm assuming you're only dealing with positive numbers. So, the answer would be 9
No. $x^2= 81$ for x= 9 or -9 but $\sqrt{81}= 9$, not -9. The square root of a number is defined as the positive root.