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wu :: forums    riddles    medium (Moderators: Eigenray, Grimbal, william wu, towr, Icarus, SMQ, ThudnBlunder)    solve 2 « Previous topic | Next topic » Pages: 1  Reply Notify of replies Send Topic Print    Author  Topic: solve 2  (Read 225 times) tony123 Junior Member     Posts: 61 solve 2   « on: Jun 29th, 2007, 6:46am » Quote Modify sqrt(5 - x) +x^2 = 5 « Last Edit: Jun 29th, 2007, 6:49am by tony123 » IP Logged jollytall Senior Riddler     Gender: Posts: 585 Re: solve 2   « Reply #1 on: Jun 29th, 2007, 12:01pm » Quote Modify if you do: sqrt(5-x) = 5-x2 then squere it (requires 5-x>0 and 5-x2>0, see backtesting later) 5-x=25-10x2+x4 then x4-10x2+x+20=0 or (x2+x-5)*(x2-x-4)=0 then from here you have four potential solutions. All the four have 5-x>0, but two have not 5-x2>0.   So the two solutions: (sqrt(21)-1)/2 and (1-sqrt(17))/2 IP Logged Pages: 1  Reply Notify of replies Send Topic Print Forum Jump: ----------------------------- riddles -----------------------------  - easy => medium   - hard   - what am i   - what happened   - microsoft   - cs   - putnam exam (pure math)   - suggestions, help, and FAQ   - general problem-solving / chatting / whatever ----------------------------- general -----------------------------  - guestbook   - truth   - complex analysis   - wanted   - psychology   - chinese « Previous topic | Next topic »

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