如何在dart中得到方程的解？X*A+B=0

import 'dart:math';

double A = 2;
double B = 5;

double equation(double x) {
  return A * x + B;
}

double findRoot(double start, double end, double precision) {
  double mid = (start + end) / 2;
  double result = equation(mid);

  if ((end - start).abs() < precision) {
    return mid;
  } else if (result > 0) {
    return findRoot(start, mid, precision);
  } else if (result < 0) {
    return findRoot(mid, end, precision);
  } else {
    return mid;
  }
}

double root = findRoot(-100, 100, 0.0001);
print('方程的解为: $root');