void test_linear(vector<int> x, vector<int> y) {
	double sumX = 0, sumY = 0, sumXY = 0, sumXSq = 0, sumYSq = 0;
	double a, b, n = x.size();

	for (int i = 0; i < x.size(); i++) {
		sumX += x[i];
		sumY += y[i];
		sumXY += x[i] * y[i];
		sumXSq += x[i] * x[i];
		sumYSq += y[i] * y[i];
	}

	a = (sumX * sumY - n * sumXY) / (sumX * sumX - n * sumXSq);
	b = (sumX * sumXY - sumXSq * sumY) / (sumX * sumX - n * sumXSq);
	cout << "a = " << a << ", b = " << b << "\n";
}