Probably will be asking a few questions in this thread throughout the days! :P
1) Given that 3+i is a root of f(x)=0 where f(x)= 2x^3+ax^2+bx-10
a) Find the other 2 roots - Which I found to be 3+- 2i. THe answer although shows that the root is 1/2 (0.5) <-- Which is what I dont understand!
b Find the value of a and b,which I found to be a: -13, b =26 (which are correct)
Thanks in advance!
FP1 Edexcel 1st Feb 2010 Watch
- Thread Starter
- 26-01-2010 19:13
- 26-01-2010 21:50
If one answer is complex, a second one must be the conjugate of that surely?
So the other root is 3 - i.
This means the third root really is 0.5
- 26-01-2010 21:55
If z is a root, so is z*.
(x - z)(x - z*)(x - t) = 2x^3 + ax^2 + bx - 10
You have to find t. Apparently, in your post you said it was 0.5.