More square roots

[citylights05]

Determine whether each number is rational or irrational. If it is irrational, find two consecutive integers between which its graph lies on the number line.

the square root of negative 81

My answer:
negative 9... it is rational

the square root of 67

My answer:
8.2 (rounded)... it is irrational, and the two consecutive integers would be 8 and 9

Can anyone confirm these ?

 

[tkhunny]

good on sqrt(67)

Try again on sqrt(-81) -- Can we use Imaginary numbers?

(-9)*(-9) = +81

 

[citylights05]

i dont understand

 

[tkhunny]

You don't understand what?

-9 is NOT the square root of -81.
-81 does NOT have a square root in the Real Numbers.
(Negative)*(Negative) = (Positive)

Maybe we're just not seeing the same problem.

Was it

sqrt(-81)

or

-sqrt(81)

It makes quite a difference.

 

[pka]

Could it have possibly been –√(81), that is, minus the square root of 81?
If so the value is –9.

 

[citylights05]

Sorry

It is -sqrt(81)...
Sorry for the confusion. I didn't know there was a difference. So it is -9 and it is rational... Right?

 

[pka]

RIGHT!

 

[citylights05]

thank you