Check whether two straight lines are parallel or not (original) (raw)

Last Updated : 23 Jul, 2025

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 a_{i}x^{2} + b_{i}x + c , 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 <bits/stdc++.h> 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 a1b2 = a2b1 if (a1b2 == a2b1) { 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

`

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