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# OCR MEI FP1 Root of Complex numbers watch

1. 1. One root Z3-15z2+76z-140 = 0 is an integer. Solve the equation.

5. The eqution Z4-8z3+20z2-72z+99= 0 has a pure imaginary root Solve the equation.

Please give me some tip on what i should do !!
Thanks a lot!

Why not try posting in a specific subject forum- you might have more luck there.

Here's a link to our subject forum which should help get you more responses.

3. (Original post by ucjs2)
1. One root Z3-15z2+76z-140 = 0 is an integer. Solve the equation.
Moved to maths - try guessing roots till you can factor out a linear factor then solve the resulting quadratic normally.
4. For the second one, try relating the coefficients to the roots. Then use the fact that there is a purely imaginary root, and the fact that all of the coefficients are real to manipulate the 4 equations you get and you can find all 4 roots this way.

(I had to have a go at this question myself as once the factor formula couldn't find any roots I couldn't not solve it could I?)
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