00:02
Okay, so the square root of negative 9 is just the square root of 9 times the square root of negative 1.
00:11
Remember that i is defined as the imaginary unit and it's equal to the square root of negative 1.
00:17
So this is just equal to 3i.
00:23
Now, if you have a problem like number 4, you have the square root of negative 3 times the square root of negative 70.
00:33
You can multiply those together and that is going to give you the square root of positive 225, which is just equal to positive 15.
00:50
For a problem like number 5, you have 2 plus the square root of negative 12 over 2.
00:59
So the first thing you want to do is rewrite that square root of negative 12.
01:05
That is just the square root of negative 4 times 3.
01:12
So that gives you 2 plus 2i radical 3 over 2.
01:20
Each term in that numerator is divisible by 2, so that will give you 1 plus i radical 3...