$\sqrt{16}=?$  

 $9^2=18$  True or false?

 $-\sqrt{144}$  

 $\sqrt{-144}$  

 $3_{\sqrt{8}}$    (cube root of 8) 

 $3_{\sqrt{-1}}$  (cube root of -1)

The area of a square painting is 81  $cm^2$  . What is the length of one side?

 $-6^2$  = ? 

 $\left(-6\right)^2$  = ?

 $\sqrt{\left(\frac{16}{81}\right)}\ \ =\ ?$