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    If I differentiate a cubic, and then factorise the resulting quadratic, I get two solutions. How do I know there isn't a missing solution?
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    because a quadratic only has two solutions?
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    (Original post by ScienceGeek1878)
    because a quadratic only has two solutions?
    Yes, but a cubic can have 3 solutions. How do I know that I'm not missing a solution?
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    (Original post by UCASLord)
    Yes, but a cubic can have 3 solutions. How do I know that I'm not missing a solution?
    A cubic can have three solutions, but what you are finding by differentiating is the MINIMUM and MAXIMUM POINTS. A cubic (any cubic) will only have TWO minimum and maximum points, which are points that have a gradient of 0.
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    (Original post by theeconomistkid)
    A cubic can have three solutions, but what you are finding by differentiating is the MINIMUM and MAXIMUM POINTS. A cubic (any cubic) will only have TWO minimum and maximum points, which are points that have a gradient of 0.
    Thanks, for some reason I thought it was possible to have 3 stationary points.
 
 
 
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