Re: quadratic multiplication

*To*: mathgroup at smc.vnet.net*Subject*: [mg84295] Re: quadratic multiplication*From*: KFUPM <hussain.alqahtani at gmail.com>*Date*: Mon, 17 Dec 2007 19:22:12 -0500 (EST)*References*: <fk2v35$n96$1@smc.vnet.net> <fk5akt$5jc$1@smc.vnet.net>

On Dec 17, 11:05 am, dh <d... at metrohm.ch> wrote: > Hi, > > we may create a rule that sets all products of u^s to zero: > > mem[y_]:=MemberQ[{u1,u2,u3,u4,u5,u6},y]; > > rules={y1_ y2_/;mem[y1]&&mem[y2]->0,y_^_/;mem[y]->0}; > > here is an example: > > c1 u1+c2 u2+ c15 u1 u5 + c146 u1 u4 u6 /. rules > > hope this helps, Daniel > > > > KFUPM wrote: > > Dear all > > > I have a very large expression which involves the multiplication of > > these variables: > > > var ={u1,u2,u3,u4,u5,u6} with some other constants. In the expression, > > i want to suppress any quadratic or higher order multiplication of > > these varibles , e.g u1*u5 or u1*u4*u6 should be zero. And since, my > > expression is huge, i want to do this automatically. Any help in this > > regard is highly appreciated. > > > Sincererly yours, > > > HMQ- Hide quoted text - > > - Show quoted text - Thanks for your reply. The rule didn't work for this term: Out[103]= \!\(\* RowBox[{\(5\/2\), " ", \(b\^4\), " ", \(x[2]\^4\), " ", RowBox[{ SuperscriptBox["u11", TagBox[\((1, 0, 0)\), Derivative], MultilineFunction->None], "[", \(x[1], x[3], t\), "]"}], " ", RowBox[{ SuperscriptBox["u13", TagBox[\((1, 0, 0)\), Derivative], MultilineFunction->None], "[", \(x[1], x[3], t\), "]"}]}]\) Please note that b is a constant. So the varibles are only u11 u13. I appreciate your help in this regard. Thanks in anticipation.