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# FP1 Edexcel 1st Feb 2010 watch

1. Hey!

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)

2. 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
3. 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.

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