Knight' Posted December 2, 2003 Share Posted December 2, 2003 Hi guys, I'm suck on a question, and I thought some of you might be able to help: Find DY/DX of y=5x(4)-x(5) (4) means power 4 etc. ok well I got DY/DX of 20x(3)-5x(4) using nx(n-1) Now it asks me to calculate the co-ordinates of the sationary points. So since gratiants of sationary points always are Zero I set DY/DX to Zero. => 20x(3)-5x(4)=0 Now i'm convinced that I have to factorise this to give me my X co-ordinates... but I can't seem to factorise it, can anyone help? There's allot more to this question, but I think I can do the rest by myself after this, I just need some help here. Thanks. Link to comment Share on other sites More sharing options...
dreamz Veteran Posted December 2, 2003 Veteran Share Posted December 2, 2003 ok, i only read about the factoring, not the rest of it. 20x^3 - 5x^4 = 0 divide by 5 4x^3 - x^4 = 0 factor out x^3 x^3(4 - x) = 0 so x^3 = 0 (triple root), 4 - x = 0 x = 0, x = 4 Link to comment Share on other sites More sharing options...
caustiK Posted December 2, 2003 Share Posted December 2, 2003 the factorization is: 5x^3 (4-x) = 0. edit: or that ^^^ - same time :) Link to comment Share on other sites More sharing options...
Knight' Posted December 2, 2003 Author Share Posted December 2, 2003 Excellent thanks, I'm hopeless at factorising... I can do all the other stuff but not the factorising :( It's something I'll have to learn ;) Thanks! Link to comment Share on other sites More sharing options...
dreamz Veteran Posted December 2, 2003 Veteran Share Posted December 2, 2003 no problem. it's not hard, you just need to see the quickest way to factor, that's all. nice simultaneous posts, caustik. :laugh: :) Link to comment Share on other sites More sharing options...
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