simplify radicals

Question

simplify:

 

1.  √-25√-9

 

2.  (6i)^2

 

3.  1/i

 

4.  -√3(√-3)

 

5.  1/2 - i

 

thanks

Answer 1

1. √(-25)√(-9) = (5i)(3i) = –15

2. (6i)^2 = (6i)(6i) = –36

3. 1/i = i/i^2 = –i

4. – √(3)√(-3) = – √(3) i√(3) = –3i

5. 1/(2–i) = (2+i)/((2+i)(2–i)) = (2+i)/5 = 2/5 + 1/5 i

Answer 2

1.

    5i . 3i = -15

 

 2 .  -36

 

 3 .   -i

 

4 .  - 3i

 

5.  1/ ( 2 - i) =  ( 2 - i )  / ( 2 +i ) ( 2 -i) = 1/3( 2- i ) = 1/6 -1/3i