I am not able to get the vertical line/horizontal line part and also this point does not esist. I tried using if statements but still cant get it right

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C++

1. The slope m of the line between the two points (x1, y1) and (x2, y2) is given by the formula
2 1
2 1
x x
y y
x
y
m






Write a program that will ask the user for the coordinates of two points and do the following:
 Determine if the two points form a line.
 Detect if the line is horizontal and alert the user.
 Detect if the line is vertical and alert the user.
 Calculate the slope of the line segment connecting them, if not 0 or undefined.
Use double-type variables for storing the coordinates and calculations made from them.
Sample Run:
Enter the coordinates of point 1 (x, y): 3 8
Enter the coordinates of point 2 (x, y): 3 8
Alert! These points do not form a line.
Sample Run:
Enter the coordinates of point 1 (x, y): 3 3
Enter the coordinates of point 2 (x, y): 7 8
The slope of the line is 1.25
Sample Run:
Enter the coordinates of point 1 (x, y): -2 9
Enter the coordinates of point 2 (x, y): 4 9
Alert! The line is horizontal.
Sample Run:
Enter the coordinates of point 1 (x, y): 5 -6
Enter the coordinates of point 2 (x, y): 5 9
Alert! The line is vertical.
Next modify the program to print the equation of the line in slope-intercept form (
y  mx  b
). Use the
appropriate “y = ” and “x = ” for horizontal and vertical lines, respectively.
Sample Run:
Enter the coordinates of point 1 (x, y): 3 5
Enter the coordinates of point 2 (x, y): 5 8
The slope of the line is 1.50
The slope-intercept form is y = 1.50x + .50

What I have tried:

#include <stdio.h>
/* function main begins program execution */
int main(void)
{
float slope, intercept;
float x1, y1, x2, y2, x3, y3;
float dx, dy;

/*coordinate phase*/
printf("Enter the coordinates of point 1: "); /* prompt for input */
scanf("%f", &x1); /*coordinate from user*/
scanf("%f", &y1); /*coordinate from user*/
printf("Enter the coordinates of point 2: "); /* prompt for input */
scanf("%f", &x2); /*coordinate from user*/
scanf("%f", &y2); /*coordinate from user*/
printf("\n");
printf("\n");

/*slope phase*/
dx = x2 - x1;
dy = y2 - y1;
slope = dy / dx;

printf("The slope of the line is = %.5f", slope); /* display result */
printf("\n");
printf("\n");

/*y intercept phase*/
/* y = mx + b*/
/*intercept b = y - m*/
intercept = y1 - slope * x1;

/*line equation phase*/
printf("The slope intercept form is: y = %.5fx %c %.5f\n", slope, (intercept < 0) ? ' ' : '+', intercept); /* display result */
printf("\n");
printf("\n");

return 0; /* indicate that program ended successfully */
} // end function main *