Re: System for which Solve and NSolve both fail
- To: mathgroup at smc.vnet.net
- Subject: [mg30578] Re: System for which Solve and NSolve both fail
- From: "Stephen P Luttrell" <luttrell at signal.dra.hmg.gb>
- Date: Thu, 30 Aug 2001 03:51:24 -0400 (EDT)
- Organization: Defence Evaluation & Research Agency
- References: <9mi1rt$54r$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
"Ben Langton" <ben at spam.bugs.me.quickmath.com> wrote in message news:9mi1rt$54r$1 at smc.vnet.net... > Hi, > > I noticed that Mathematica seems unable to solve this system of equations : > > 3^x + 3^y = 90 > > x + y = 6 > >... You could try the following type of approach: 1. Use ImplicitPlot to see roughly where the solutions lie. << Graphics`ImplicitPlot` ImplicitPlot[{3^x + 3^y == 90, x + y == 6}, {x, 0, 10}, {y, 0, 10}]; 2. Use FindRoot to accurately locate the solution(s), given approximate starting point(s). FindRoot[{3^x + 3^y == 90, x + y == 6}, {x, 2.5}, {y, 1.5}] and FindRoot[{3^x + 3^y == 90, x + y == 6}, {x, 1.5}, {y, 2.5}] -- Stephen P Luttrell QinetiQ, Malvern, U.K.