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    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!
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    Sorry you've not had any responses about this.

    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.


    (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.

    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?)
    Answers: Don't cheat
     Z= \pm 3i, 4\pm \sqrt 5
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