# Questions tagged [equation-solving]

Questions on the analytic and numerical equation solving functions of Mathematica (Solve, Reduce, NSolve, FindRoot, DSolve, RSolve, etc.).

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### Figure out original balance with only the amount of loss and amount of decrease [closed]

I'm sure there is an easy solution to this, but I can't remember how to set something like this up. I was thinking a differential equation may be the answer. For context, this relates to stocks, but ...
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### Simplifying an equation in which all the terms are integrals with respect to the same variable

I have an equation in the following form: Integrate[A[x], x] + Integrate[B[x], x] == Integrate[C[x],x] How can I simplify this equation to get: ...
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### Stability analysis of coupled ODE's

I'd like to reproduce Panel A of Figure 7 (red curve) of this paper, which represents the steady-state solutions of four coupled ODE's, and verify this claim that the diagonal branch in the Z-shape ...
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### FindRoot doesn't find root

I am facing a problem that my FindRoot doesn't find the actual roots. I am trying to make a loop that iterates my parameter sets (U0,X0,\Sigma0) to find sets that satisfy some conditions. Here is my ...
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### What are some techniques used to speed up numerical solving (with NSolve)?

I have a rather complicated set of equation to solve, as shown in the code below: ...
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### Want a DiscretePlot of an NSolve that uses a parameter n

Let's say I want to solve f[n,R]==0 with respect to R for n=1,2,3,... (up to some upper ...
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I have this mathematic problem: (124164a/300b/2360/.85)+(124164a/25b/2360/.85)+(124164a/55b/2360/.85)=3.81=(a/b/2360/.85) And this is the result: a≈87.4514, b≈0.0114422 I payed for WolframAlpha Pro ...
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### Findroot to evaluated a function that become multivalued and varying of a parameter

I am having problem in solving this equation: s[t_?NumericQ, l_?NumericQ] :=FindRoot[s - Sin[t - (l*s)] == 0, {s, t, l}, Method -> "Automatic"][[1, 2]] ...
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### Why does this ConditionalExpression appear? [closed]

I am new to Mathematica. Could anyone help explain why ws > 0 appears in the solution? How to define symbolic variables' range? Thanks! EDIT to include code <...
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### FindMinimum/FindRoot failed to converge

I have a function SQ where it is also determined by sig. For b=0.1 and ...
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### Strange behavior of NDSolve (Error NDSolve::ntdvdae)

i discovered a weird behavior using NDSolve to solve a set of differential equations. Let me outline my problem: I need to solve a set of differential equations. These are equations of motion ...
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### How can I find the only real and then the smallest root of a 4th-order polynomial?

I just want to solve the below polynomial for real roots only, where I have mentioned the conditions on all variables, a,d,m,L. ...
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### I need help with a basic Solve question

I have the following two conditions: Dc == t0^2 Dp == t1^2 The actual formulas I'm trying to solve are more complex, but this is the essence of the relations. I ...
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### How to use NSolve while specifying the range of one variable

I have an equation that uses three variables that I have defined as follows: b[l_, m_, lt_] := 0.025 * (((1 - m)*l)^(-1/2))*((1 - m)*lt) - 5. After this definition, ...
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### Error: "ReplaceAll: ... is neither a list of replacement rules nor a valid dispatch table, and so cannot be used for replacing." when solving a root

I have this code: ...