Question

How to find the roots of a quadratic equation in PHP

Answer 1

function quadratic_equation_roots($a, $b, $c) {
    $discriminant = ($b * $b) - (4 * $a * $c);
 
    if ($discriminant > 0) {
        $root1 = (-$b + sqrt($discriminant)) / (2 * $a);
        $root2 = (-$b - sqrt($discriminant)) / (2 * $a);
        echo "root1 = " . $root1 . "\nroot2 = " . $root2 . "\n";
    }
    else if($discriminant == 0) {
        $root1 = $root2 = -$b / (2 * $a);
        echo "root1 = root2 = " . $root1 . "\n";
    }
    else if($discriminant < 0) {
        $real = -$b / (2 * $a);
        $imaginary = sqrt(-$discriminant) / (2 * $a);
        echo "root1 = " . $real . "+" . $imaginary . "i\nroot2 = " . $real . "-" . $imaginary . "i\n";
    }
}
 

$a = 3;
$b = 5;
$c = -9;
 
quadratic_equation_roots($a, $b, $c);
echo "\n";
 
$a = 3;
$b = 5;
$c = 7;
quadratic_equation_roots($a, $b, $c);
echo "\n";
 
$a = 2;
$b = 4;
$c = 2;
quadratic_equation_roots($a, $b, $c);
 

 
 
/*
run:
 
root1 = 1.0887604324451
root2 = -2.7554270991118

root1 = -0.83333333333333+1.2801909579781i
root2 = -0.83333333333333-1.2801909579781i

root1 = root2 = -1
 
*/

 

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