## Linear Equation

A linear equation is expressed by formula
$a1\cdot v1+a2 \cdot v2+a3 \cdot v3+\ldots +an \cdot vn+c=0$, where a1,
a2, a3, ..., an, c are constant coefficients, and v1, v2, v3, ..., vn
are scalar equation variables. You can create a linear equation by
calling

```cpp
constraint_item GCE_AddLinearEquation(GCE_system gSys, const double * a, 
                                     const var_item * v, 
                                           size_t n, 
                                           double c),
```

that returns a descriptor of the linear equation registered in the
**gSys** system.

Initial method call data are given below:

-   **gSys** is a constraint system;

-   **a** is an array of constant coefficients for variables;

-   **v** is an array of linear equation variables;

-   **n** is a number of linear equation variables;

-   **с** is a constant coefficient c that is not multiplied by any
    variable.