# Tagged Questions

560 views

### Mathematica isn't sure whether a sum of two positives is positive or not

Mathematica is not able to tell whether a summation of two positive expressions is positive or not. Which is very strange. My three symbolic arguments, $x$, $y$, and $z$, are all real numbers bounded ...
72 views

### Is there a change in V10 with Solve and exponents?

I've encountered a strange problem with V10. I can't quite nail it down, but the Solve seems to be unable to solve equations that it could in previous versions. ...
55 views

### How to figure out whether a nonlinear inequality holds or not

I have an inequality consisted only of seven parameters as follows: $(1 + g)^{-(m+w)}\big[\big\{a+(1-a)(1 + g)^m\big\}(1 + p q)Q - (1 + g)^w \big\{(1 + g)^m (1 + q)-(1-p)q\big\} Q\big] < 0$ ...
180 views

### Counting Real roots

I'm interested on how to count the number of real roots of a random polynomials in an instant, how to put the result in a table and how to plot it in a graph.I generated 1 million random polynomials ...
676 views

### What is the equation to plot a vertical line?

Please help. Trying to find area between three curves, e^-x, x = 2, y = 1. Can't find out how to plot x = 2. Don't want to use ...
77 views

### FindRoot kills kernel

Bug introduced in 7.0.1 or earlier. Persists through at least 10.0.0. I'm having problems with FindRoot killing the kernel. In my real application, I want to FindRoot on a black-box function ...
68 views

### Solving a two point boundary problem for a piecewise system of equations

I'm trying to solve a two point boundary value problem with a piecewise system of equations like: ...
97 views

### How to manipulate with external data?

I have a .txt file which contains a lot of triples (a, b, c) (one per row) which should be coefficients of my equation ax^2+bx+c=0. I want to include each triple in .nb file and solve each equation. ...
96 views

### How can I produce a list of solutions for a function which is updated with updated variables using for loop?

I need to loop over a set of equations, solving for X and adding the new X value to the old X value at each step. The output I need is a list ...
167 views

### How do I feed data points into an equation to solve NUMERICALLY?

I start with this equation and solve it numerically for $z(x,y)$ in the range $1 < x < 5$ and $1 < y < 5$: $$\frac{3}{xyz} - 2x - 3y - 5z = 0$$ Then using the data points of $z$ above, ...
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215 views

### Is there a relatively quick way to solve my integer-valued equation?

This is a very simple problem. It can be solved by nested Forloops that exhaustively test every possible case, throwing out all non-solutions. Find all the ...
155 views

### How to find the integer solution number of a linear system with inequalities?

I have the following system with mixed equality and inequalities defined as: ...
54 views

### Error when using EquationTrekker

I just got to know EquationTrakker because I need to do phase graphs for my classes. When I load it ...
53 views

### What methods does Solve use?

Could you tell me which method that Solve applies to solve linear and polynomials equations?
96 views

### NDSolve solution violates initial conditions

I have the following code: ...
202 views

### How can I only draw outer common tangent to two circles?

I have code worked for drawing common tangent lines to two circles(http://en.wikipedia.org/wiki/Tangent_lines_to_circles), now I want to delete the inner common tangent lines, how? ...