Why gives Plot[GTK,{q,o,30}] negat. min. at q=15 ? (GTK:=1/3 q^2 - 10 q + 100)

*To*: mathgroup at smc.vnet.net*Subject*: [mg2244] Why gives Plot[GTK,{q,o,30}] negat. min. at q=15 ? (GTK:=1/3 q^2 - 10 q + 100)*From*: txp at pi.net (JanHolland)*Date*: Wed, 18 Oct 1995 01:54:59 -0400*Organization*: txp

Hello, Say ATC = Average Total Cost := 1/3 q^2 - 10 q + 100 When I give Plot[ATC,{q,0,30}] the resulting graph gives a minimum below the X-axis at about q=15 When I give q=15 and N[ATC] it evaluates correctly to GTK=25. Does anyone know what am I doing wrong ? Thanks for any effort you take ! ------------- GMT 16.15 Jan Holland ----------- Jan Holland txp at pi.net "A fact is a broken dream"