What is the slope of parallel lines?

Do you know what is the value of slope of parallel lines? Do parallel lines have any slope? The answer is yes parallel lines has slope. But we should see that both are equal or not. This we will come to know while studying coordinate geometry.

Slopes of parallel lines explained

I hope everyone is aware of what are the parallel lines? So next we should know what is the meaning of slope. Slope of a line is nothing but ratio of the difference of y-coordinates to the x-coordinates of any two points on the given line. Another definition we give as if θ is the angle then we call tanθ as slope of the line.


If the given line is in the form of ax+by+c=0 then slope of that line is given by –a/b. we should keep in mind that any parallel lines differ only by constant term. For example: ax+by+r=0 and ax+by+p=0 are parallel lines. Observe the two lines clearly we find the only difference is constant.

How to find slope of parallel lines?

Directly at a time, we cannot find slope of parallel lines. First we should find the slope of any one line out of two given parallel lines. For finding slope, we can use any one method. After finding first line slope then find out second line slope also. After getting slopes of both the lines if we observe both the slopes will be equal (same). So finally we say that the slopes of parallel lines are equal.

Slopes of parallel lines explained

If you want, you can check whether slopes of parallel lines are equal or not by taking any two parallel lines. See the example you can know how to check.

For example:

3x+4y+5=0 and 3x+4y+9=0 be the parallel lines.

Slope of 3x+4y+5=0 is -3/4

Slope of 3x+4y+9=0 is -3/4

It is very clear that both slopes are equal. I hope that all of you understood, what is the value of slope of parallel lines.

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