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    From Page 30 of the C3 Revision Guide

    The equation x^3-4x^2-17x+50=0 has 3 real roots. Find intervals in the form (N, N+1) where N is an integer, in which each root lies.

    Please help
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    Let f(x) = x^3 - 4x^2 - 17x + 50. Then

    -x | f(x)
    -4 | -10
    -3 | 38
    -2 | 60
    -1 | 62
    -0 | 50
    -1 | 30
    -2 | 8
    -3 | -10
    -4 | -18
    -5 | -10
    -6 | 20

    f changes sign in the intervals (-4, -3), (2, 3) and (5, 6).
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    Do they let you use iteration in these Qs?
    How do you know what domain to use?
    Do we just assume they'd give us say -10<x<10 or something?
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    (Original post by Jonny W)
    Let f(x) = x^3 - 4x^2 - 17x + 50. Then

    -x | f(x)
    -4 | -10
    -3 | 38
    -2 | 60
    -1 | 62
    -0 | 50
    -1 | 30
    -2 | 8
    -3 | -10
    -4 | -18
    -5 | -10
    -6 | 20

    f changes sign in the intervals (-4, -3), (2, 3) and (5, 6).
    how did u knw 2 put those values in?
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    (Original post by mackin boi)
    how did u knw 2 put those values in?
    I started at x = 0 and worked outwards in both directions until I had found three sign-changes.
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    (Original post by Jonny W)
    I started at x = 0 and worked outwards in both directions until I had found three sign-changes.
    :confused: wat happens if it was inbetween 100 and 101???
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    (Original post by mackin boi)
    :confused: wat happens if it was inbetween 100 and 101???
    You'd have used common sense as you see if the values of the function you get from a certain value of x are nowhere near 0 you obviously need to change dramatically. You could also use a graph.
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    grafs are betta arent they?
 
 
 
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