# How to write a simple python code to find the intersection point between two straight lines ?

Published: June 21, 2019

Example of how to write a simple python code to find the intersection point between two straight lines:

### Plot the lines

````import matplotlib.pyplot as plt`
`import numpy as np`

`m1, b1 = 1.0, 2.0 # slope & intercept (line 1)`
`m2, b2 = 4.0, -3.0 # slope & intercept (line 2)`

`x = np.linspace(-10,10,500)`

`plt.plot(x,x*m1+b1)`
`plt.plot(x,x*m2+b2)`

`plt.xlim(-2,8)`
`plt.ylim(-2,8)`

`plt.title('How to find the intersection of two straight lines ?', fontsize=8)`

`plt.grid(linestyle='dotted')`

`plt.savefig("two_straight_lines_intersection_point_01.png", bbox_inches='tight')`
```

### Find the intersection point

````xi = (b1-b2) / (m2-m1)`
`yi = m1 * xi + b1`

`print('(xi,yi)',xi,yi)`
```

returns (xi,yi) 1.6666666666666667 3.666666666666667:

### Plot the intersection point

````plt.scatter(xi,yi, color='black' )`

`plt.savefig("two_straight_lines_intersection_point_02.png", bbox_inches='tight')`
```

### Another example

````import matplotlib.pyplot as plt`
`import numpy as np`

`m1, b1 = 0.1, 2.0 # slope & intercept (line 1)`
`m2, b2 = 2.0, -3.0 # slope & intercept (line 2)`

`x = np.linspace(-10,10,500)`

`plt.plot(x,x*m1+b1,'k')`
`plt.plot(x,x*m2+b2,'k')`

`plt.xlim(-2,8)`
`plt.ylim(-2,8)`

`plt.title('How to find the intersection of two straight lines ?', fontsize=8)`

`xi = (b1-b2) / (m2-m1)`
`yi = m1 * xi + b1`

`print('(xi,yi)',xi,yi)`

`plt.axvline(x=xi,color='gray',linestyle='--')`
`plt.axhline(y=yi,color='gray',linestyle='--')`

`plt.scatter(xi,yi, color='black' )`

`plt.savefig("two_straight_lines_intersection_point_03.png", bbox_inches='tight')`
```

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