How to Write Linear Equations?
Read,5 minutes
An equation presented in slope-intercept form is written as y = mx + b
Where m is the slope of the line and b is the y-intercept. If you know the slope and the y-intercept, you can use this equation to write a line equation.
Example
Find the equation of the line that passes through the points (−1,0) and (0,3) .
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Solution:
We should find the b-value and the y-intercept, to do that, so we select two points on the line:
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Now, determine the slope between the 2 points:
m = y2 − y1x2 − x1 = 0 − 3−1 − 0 = −3−1 = 3
The b-value can be found by just looking at the graph:
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⇒ b = 3
Now, we can use the equation y = mx + b and write the line's equation:
y = mx + b ⇒ y = 3x + 3
In a lot of cases, the value of b isn’t read so easily. In that case, or in cases where you are not sure if the line really crosses the y-intercept at this particular point, b can be calculated by solving the equation for b, then substituting x and y with one of the two points.
The previous example can be used to explain this:
- The two points are (−1 , 0), and (0 , 3). We determined the slope from these two points: m = 3
- Now we have the equation: y = 3x + b
From that the equation can be solved for b: b = y − 3x
- Also, if we input the values from the second point (0 , 3), we have: b = 3 − 3(0) = 3
- Finally, we can write the line equation: y = 3x +3
Summary:
Writing linear equations:
- Step1: Determine the slope, m. This can be done by utilizing the slope formula to get the slope between two known points on the line.
- Step2: Determine the y-intercept. In order to do this, simply substitute the slope and the (x , y) coordinates of a point on the line in the slope-intercept formula and then calculate b.
- Step3: Once you have m and b, you can enter them into the slope-intercept equation and find the line equation.
Free printable Worksheets
Exercises for Writing Linear Equations
1) Find the line equation of the line passing through (10,9)(11,0) ⇒
2) Find the line equation of the line passing through (8,7)(9,−5) ⇒
3) Find the line equation of the line passing through (7,10)(8,−6) ⇒
4) Find the line equation of the line passing through (9,5)(10,3) ⇒
5) Find the line equation of the line passing through (10,2)(11,3) ⇒
6) Find the line equation of the line passing through (1,4)(2,2) ⇒
7) Find the line equation of the line passing through (7,3)(8,5) ⇒
8) Find the line equation of the line passing through (2,9)(3,5) ⇒
9) Find the line equation of the line passing through (3,6)(4,−4) ⇒
10) Find the line equation of the line passing through (5,1)(6,−3) ⇒
1) Find the line equation of the line passing through
(10,9)(11,0) ⇒ m=0 − 911 − 10=−9 ⇒ y−9=m(x−10) ⇒ y=−9x + 99
2) Find the line equation of the line passing through (8,7)(9,−5) ⇒ m=−5 − 79 − 8=−12 ⇒ y−7=m(x−8) ⇒ y=−12x + 103
3) Find the line equation of the line passing through (7,10)(8,−6) ⇒ m=−6 − 108 − 7=−16 ⇒ y−10=m(x−7) ⇒ y=−16x + 122
4) Find the line equation of the line passing through (9,5)(10,3) ⇒ m=3 − 510 − 9=−2 ⇒ y−5=m(x−9) ⇒ y=−2x + 23
5) Find the line equation of the line passing through (10,2)(11,3) ⇒ m=3 − 211 − 10=1 ⇒ y−2=m(x−10) ⇒ y=x − 8
6) Find the line equation of the line passing through (1,4)(2,2) ⇒ m=2 − 42 − 1=−2 ⇒ y−4=m(x−1) ⇒ y=−2x + 6
7) Find the line equation of the line passing through (7,3)(8,5) ⇒ m=5 − 38 − 7=2 ⇒ y−3=m(x−7) ⇒ y=2x − 11
8) Find the line equation of the line passing through (2,9)(3,5) ⇒ m=5 − 93 − 2=−4 ⇒ y−9=m(x−2) ⇒ y=−4x + 17
9) Find the line equation of the line passing through (3,6)(4,−4) ⇒ m=−4 − 64 − 3=−10 ⇒ y−6=m(x−3) ⇒ y=−10x + 36
10) Find the line equation of the line passing through (5,1)(6,−3) ⇒ m=−3 − 16 − 5=−4 ⇒ y−1=m(x−5) ⇒ y=−4x + 21
Writing Linear Equations Quiz