Function linear2

linear2(
    a: number | ((t: number) => number),
    b: number | ((t: number) => number),
    c: number | ((t: number) => number),
): ChalkboardODE
Defines a second-order linear scalar ODE: y'' = a(t)y' + b(t)y + c(t).
Parameters
- a: number | ((t: number) => number)
  Coefficient a(t) or constant a.
- b: number | ((t: number) => number)
  Coefficient b(t) or constant b.
- c: number | ((t: number) => number)
  Coefficient c(t) or constant c.
Returns ChalkboardODE
Example
```
const ode = Chalkboard.diff.linear2(-1, -4, 0);
const derivative = ode.rule(0, [3, 2]); // Evaluates a second-order linear equation
```
- Defined in Chalkboard.diff.ts:462