# Check whether two straight lines are parallel or not

Last Updated : 07 Feb, 2022

Given equations of two lines (a1, b1, c1) and (a2, b2, c2) such that (ai, bi, ci) are the coefficients of X2, X and a constant term of the straight line respectively, in the general equation , the task is to check if both the straight lines are parallel or not. If they are found to be parallel, then print “Yes”. Otherwise, print “No”.

Examples:

Input: a1 = -2, b1 = 4, a2 = -6, b2 = 12
Output: Yes
Explanation:
The slope of both lines are equal i.e., a1/b1 = a2/ b2 = -2.

Input: a1 = 11, b1 = 3, a2 = 7, b2 = -10
Output: No
Explanation:
The slope of both lines are not equal i.e., a1/b1? a2/b2.

Approach: To check if two lines are parallel to each other or not, the idea is to compare the slope of the given lines. If the slope of the given lines is equal then the given lines are parallel. Therefore, print “Yes” else print “No”.

Below is the implementation of the above approach:

## C++

 `// C++ program for the above approach``#include ``using` `namespace` `std;` `// Function to check if two lines``// are parallel or not``void` `parallel(``float` `a1, ``float` `b1,``              ``float` `c1, ``float` `a2,``              ``float` `b2, ``float` `c2)``{``    ``// If slopes are equal``    ``// then -(a1 / b1) = -(a2 / b2)``    ``// which is a1*b2 = a2*b1``    ``if` `(a1*b2 == a2*b1) {``        ``cout << ``"Yes"``;``    ``}``    ``else` `{``        ``cout << ``"No"``;``    ``}``}` `// Driver Code``int` `main()``{``    ``float` `a1 = -2, b1 = 4, c1 = 5;``    ``float` `a2 = -6, b2 = 12, c2 = 6;` `    ``// Function Call``    ``parallel(a1, b1, c1, a2, b2, c2);` `    ``return` `0;``}`

## Java

 `// Java program to implement ``// the above approach ``import` `java.util.*;``class` `GFG``{` `// Function to check if two lines``// are parallel or not``static` `void` `parallel(``float` `a1, ``float` `b1,``              ``float` `c1, ``float` `a2,``              ``float` `b2, ``float` `c2)``{``  ` `    ``// If slopes are equal``    ``// then (-(a1 / b1)) == (-(a2 / b2))``    ``// which is a1*b2 = a2*b1``    ``if` `(a1*b2 == a2*b1) ``    ``{``        ``System.out.println(``"Yes"``);``    ``}``    ``else``    ``{``         ``System.out.println(``"No"``);``    ``}``}` `// Driver Code``public` `static` `void` `main(String args[])``{``    ``float` `a1 = -``2``, b1 = ``4``, c1 = ``5``;``    ``float` `a2 = -``6``, b2 = ``12``, c2 = ``6``;` `    ``// Function Call``    ``parallel(a1, b1, c1, a2, b2, c2);``}``}` `// This code is contributed by splevel62.`

## Python3

 `# Python program to implement``# the above approach`  `# Function to check if two lines``# are parallel or not``def` `parallel(a1, b1, c1, a2, b2, c2):``  ` `    ``# If slopes are equal``    ``# then ((-(a1 / b1)) == (-(a2 / b2)))``    ``# which is a1*b2 = a2*b1``    ``if` `a1``*``b2``=``=``a2``*``b1:``        ``print``(``"Yes"``);``    ``else``:``        ``print``(``"No"``);` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ``a1 ``=` `-``2``; b1 ``=` `4``; c1 ``=` `5``;``    ``a2 ``=` `-``6``; b2 ``=` `12``; c2 ``=` `6``;` `    ``# Function Call``    ``parallel(a1, b1, c1, a2, b2, c2);` `# This code is contributed by 29AjayKumar`

## C#

 `// C# program to implement``// the above approach``using` `System;``class` `GFG ``{``  ` `// Function to check if two lines``// are parallel or not``static` `void` `parallel(``float` `a1, ``float` `b1,``              ``float` `c1, ``float` `a2,``              ``float` `b2, ``float` `c2)``{``  ` `    ``// If slopes are equal``    ``// then (-(a1 / b1)) == (-(a2 / b2))``    ``// which is a1*b2 = a2*b1``    ``if`  `(a1*b2 == a2*b1)  ``    ``{``        ``Console.Write(``"Yes"``);``    ``}``    ``else``    ``{``         ``Console.Write(``"No"``);``    ``}``}` `// Driver Code``public` `static` `void` `Main()``{``    ``float` `a1 = -2, b1 = 4, c1 = 5;``    ``float` `a2 = -6, b2 = 12, c2 = 6;` `    ``// Function Call``    ``parallel(a1, b1, c1, a2, b2, c2);``}``}` `// This code is contributed by susmitakundugoaldanga.`

## Javascript

 ``

Output
`Yes`

Time Complexity: O(1)
Auxiliary Space: O(1)

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