# PHP Program - Find Roots of a Quadratic Equation

A standard form of a quadratic equation is:

ax2 + bx + c = 0

Where:

a, b and c are real numbers and a ≠ 0.

Roots of the equation are: ### For Example:

The roots of equation x2 + 5x + 4 = 0 is The roots of the equation will be imaginary if D = b2 - 4ac < 0. For example - the roots of equation x2 + 4x + 5 = 0 will be ### Example: Calculate roots of a Quadratic equation

In the example below, a function called roots is created which takes a, b and c as arguments to calculate the roots of the equation ax2 + bx + c = 0.

```<?php
function roots(\$a, \$b, \$c) {
\$D = \$b*\$b - 4*\$a*\$c;
if (\$D >= 0){
\$x1 = (-\$b + sqrt(\$D))/(2*\$a);
\$x2 = (-\$b - sqrt(\$D))/(2*\$a);
echo "Roots are: \$x1, \$x2 \n";
} else {
\$x1 = -\$b/(2*\$a);
\$x2 = sqrt(-\$D)/(2*\$a);
echo "Roots are: \$x1 ± \$x2 i \n";
}
}

echo "Equation is x*x+5x+4=0\n";
roots(1,5,4);
echo "\nEquation is x*x+4x+5=0\n";
roots(1,4,5);
?>
```

The above code will give the following output:

```Equation is x*x+5x+4=0
Roots are: -1, -4

Equation is x*x+4x+5=0
Roots are: -2 ± 1 i
```

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