What is a model in the mathematical sense

Function as the basis of the model

Predicting the price of an apartment based on its area using a linear function: $ŷ = w x + b$

 
<?php

require_once __DIR__ '/code.php';

$model = new LinearModel(2.00.0);
echo 
$model->predict(3.0);
Result: Memory: 0.002 Mb Time running: 0.001 sec.
6

Explanation: $2 * 3 + 0 = 6$
By formula: $ŷ = 2 x + b$