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MathGroup Archive 2001

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Re: help: how do you solve a less-or-equal equation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31010] Re: [mg31001] help: how do you solve a less-or-equal equation
  • From: BobHanlon at aol.com
  • Date: Tue, 2 Oct 2001 01:20:45 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 2001/10/1 3:26:39 AM, kroosu at tref.nl writes:

>i'm trying the mathematica demo by doing some basic mathematics.
>
>at the moment i'm having problems with a less-or-equal equation.
>Solve[a <= b,x] (with a and b as functions of x) gives an error,
>saying it's not a well-formed equation.
>appearently Solve cant handle the less-than sign.
>how do you solve an equation like this in mathematica?
>
>and can i assign the value to the variable automaticly?
>

a[x_] := 7x^2-6x+4;
b[x_] := 6x^2-3x+2;

Plot[{a[x]-b[x]}, {x, 0, 2.5}];

Solve[a[x]-b[x]==0, x]

{{x -> 1}, {x -> 2}}

x /. %

{1, 2}

Needs["Graphics`InequalityGraphics`"];

InequalityPlot[{a[x]-b[x] <= y <=0}, {x, 0, 3}, {y, -1, 1}, 
    ImageSize == 300];

Needs["Algebra`InequalitySolve`"];

InequalitySolve[a[x]-b[x] <= 0, x]

1 <= x <= 2

{%[[1]], %[[5]]}

{1, 2}

Cases[%%, _?NumericQ]

{1, 2}


Bob Hanlon
Chantilly, VA  USA


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