SOLUTION: The question is : For i = the square root of -1, if 3i (2 + 5i) = x + 6i, then x = ? I came up with x = 15, however, the test answer says x = -15. I am confused...how can you

Algebra ->  Square-cubic-other-roots -> SOLUTION: The question is : For i = the square root of -1, if 3i (2 + 5i) = x + 6i, then x = ? I came up with x = 15, however, the test answer says x = -15. I am confused...how can you       Log On


   



Question 377975: The question is :
For i = the square root of -1, if 3i (2 + 5i) = x + 6i, then x = ?
I came up with x = 15, however, the test answer says x = -15. I am confused...how can you get the square root of a negative # and it be a negative #?

Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
3i%282+%2B+5i%29 simplifies to 6i+%2B+15i%5E2 or -15+%2B+6i --> x = -15.
The square root of a negative number is not defined on the real axis. This is why mathematicians created the number i+=+sqrt%28-1%29. For example, sqrt%28-9%29+=+3i.