Re: why doesn't the range on this interval match the plot range?

*To*: mathgroup at smc.vnet.net*Subject*: [mg66431] Re: why doesn't the range on this interval match the plot range?*From*: Bill Rowe <readnewsciv at earthlink.net>*Date*: Fri, 12 May 2006 02:03:15 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

On 5/11/06 at 2:15 AM, chris at chiasson.name (Chris Chiasson) wrote: >Parabola[x_]=4x^2+53x+160 >BeginPoint=-8; >EndPoint=-5; >Plot[Parabola[x],{x,BeginPoint,EndPoint}] >Parabola[Interval[{BeginPoint,EndPoint}]] Because Mathematica substitutes the entire interval for x to your function not just the interval end points. That is In[26]:= a=4Interval[{-8,-5}]^2 Out[26]= Interval[{100,256}] Note because of the minus sign, the result of Interval[{(-8}^2,(-5)^2}] is Interval[{5^2, 8^2}]. That is for the first term, the end points are in "reverse" order from what you are expecting. In[27]:= b=53Interval[{-8,-5}] Out[27]= Interval[{-424,-265}] In[28]:= a+b+160 Out[28]= Interval[{-164,151}] while In[29]:= 4x^2+53 x+160/.x\[Rule]-5 Out[29]= -5 and In[30]:= 4x^2+53 x+160/.x\[Rule]-8 Out[30]= -8 -- To reply via email subtract one hundred and four