Check if given two straight lines are identical or not

Given two straight lines with co-efficients of their equations a1x + b1y + c1 = 0 and a2x + b2y + c2 = 0 respectively, the task is to check if the straight lines are identical or not. 
Examples:

Input: a1 = -2, b1 = 4, c1 = 3, a2 = -6, b2 = 12, c2 = 9 
Output: The given straight lines are identical
Input: a1 = 12, b1 = 3, c1 = 8, a2 = 7, b2 = -12, c2 = 0 
Output: The given straight lines are not identical

Approach: 

1. Given equations, 
   a1x + b1y + c1 = 0 
   a2x + b2y + c2 = 0
   
2. converting them to slope intercept form, we get 
   y = (-a1/b1)x +(-c1/b1) 
   y = (-a2/b2)x +(-c2/b2)
   
3. now, if the lines are identical then there slope and intercepts must be equal, 
   so, 
   -a1/b1 = -a2/b2 
   or, a1/a2 = b1/b2
   also, 
   -c1/b1 = -c2/b2 
   so, c1/c2 = b1/b2
   
4. So, if two given straight lines are identical then there co-efficients should be proportional. 
   
   

Below is the implementation of the above approach

C++

// C++ program to check if
// given two straight lines
// are identical or not

#include <bits/stdc++.h>
using namespace std;

// Function to check if they are identical
void idstrt(double a1, double b1,
            double c1, double a2,
            double b2, double c2)
{
    if ((a1 / a2 == b1 / b2)
        && (a1 / a2 == c1 / c2)
        && (b1 / b2 == c1 / c2))
        cout << "The given straight"
             << " lines are identical"
             << endl;

    else
        cout << "The given straight"
             << " lines are not identical"
             << endl;
}

// Driver Code
int main()
{
    double a1 = -2, b1 = 4,
           c1 = 3, a2 = -6,
           b2 = 12, c2 = 9;
    idstrt(a1, b1, c1, a2, b2, c2);
    return 0;
}

Java

// Java program to check if
// given two straight lines
// are identical or not
class GFG
{

// Function to check if they are identical
static void idstrt(double a1, double b1,
                    double c1, double a2,
                    double b2, double c2)
{
    if ((a1 / a2 == b1 / b2)
        && (a1 / a2 == c1 / c2)
        && (b1 / b2 == c1 / c2))
        System.out.println( "The given straight"
        +" lines are identical");

    else
        System.out.println("The given straight"
            + " lines are not identical");
}

// Driver Code
public static void main(String[] args)
{
    double a1 = -2, b1 = 4,
            c1 = 3, a2 = -6,
            b2 = 12, c2 = 9;
    idstrt(a1, b1, c1, a2, b2, c2);
}
}

// This code has been contributed by 29AjayKumar

Python3

# Python3 program to check if
# given two straight lines
# are identical or not

# Function to check if they are identical
def idstrt(a1, b1, c1, a2, b2, c2):
    if ((a1 // a2 == b1 // b2) and
        (a1 // a2 == c1 // c2) and
        (b1 // b2 == c1 // c2)):
        print("The given straight lines",
                         "are identical");
    else:
        print("The given straight lines",
                     "are not identical");

# Driver Code
a1, b1 = -2, 4
c1, a2 = 3,-6
b2, c2 = 12,9
idstrt(a1, b1, c1, a2, b2, c2)

# This code is contributed
# by mohit kumar

C#

// C# program to check if
// given two straight lines
// are identical or not
using System;

class GFG
{

// Function to check if they are identical
static void idstrt(double a1, double b1,
                    double c1, double a2,
                    double b2, double c2)
{
    if ((a1 / a2 == b1 / b2)
        && (a1 / a2 == c1 / c2)
        && (b1 / b2 == c1 / c2))
        Console.WriteLine( "The given straight"
        +" lines are identical");

    else
        Console.WriteLine("The given straight"
            + " lines are not identical");
}

// Driver Code
public static void Main(String[] args)
{
    double a1 = -2, b1 = 4,
            c1 = 3, a2 = -6,
            b2 = 12, c2 = 9;
    idstrt(a1, b1, c1, a2, b2, c2);
}
}

// This code contributed by Rajput-Ji

PHP

<?php

// PHP program to check if
// given two straight lines
// are identical or not


// Function to check if they are identical
function idstrt($a1, $b1,
            $c1, $a2,
            $b2, $c2)
{
    if (($a1 / $a2 == $b1 / $b2)
        && ($a1 / $a2 == $c1 / $c2)
        && ($b1 / $b2 == $c1 / $c2))
        echo "The given straight lines are identical","\n";

    else
        echo "The given straight lines are not identical","\n";
}

    // Driver Code
    $a1 = -2; $b1 = 4;
    $c1 = 3; $a2 = -6;
    $b2 = 12; $c2 = 9;
    idstrt($a1, $b1, $c1, $a2, $b2, $c2);

    // This code is contributed by Ryuga

?>

Javascript

<script>

// javascript program to check if
// given two straight lines
// are identical or not


// Function to check if they are identical
function idstrt(a1 , b1,
                    c1 , a2,
                    b2 , c2)
{
    if ((a1 / a2 == b1 / b2)
        && (a1 / a2 == c1 / c2)
        && (b1 / b2 == c1 / c2))
        document.write( "The given straight"
        +" lines are identical");

    else
        document.write("The given straight"
            + " lines are not identical");
}

// Driver Code


var a1 = -2, b1 = 4,
        c1 = 3, a2 = -6,
        b2 = 12, c2 = 9;
idstrt(a1, b1, c1, a2, b2, c2);

// This code contributed by Princi Singh

</script>

Output:

The given straight lines are identical

Time Complexity: O(1)

Auxiliary Space: O(1)