Function linear1

linear1(
a: number | ((t: number) => number),
b: number | ((t: number) => number),
): ChalkboardODE
Defines a first-order linear scalar ODE: y' = a(t)y + b(t).
Parameters
- a: number | ((t: number) => number)
  Coefficient a(t) or constant a.
- b: number | ((t: number) => number)
  Coefficient b(t) or constant b.
Returns ChalkboardODE
Example
```
const ode = Chalkboard.diff.linear1(-2, 1);
const derivative = ode.rule(0, [3]); // Returns [-5]
```
- Defined in Chalkboard.diff.ts:444