Example

Title: Slope & Line Segment

Grade: 8-a Lesson: S3-L4

Explanation: Hello Students, time to learn examples. Let us take turns and read each example. Explain each step. Pay special attention to steps and pictures and communicate in your own words.

Examples:

To find the equation of the line passing through the points (1, -2) and (4, -5)

Step 1a

First, to find the slope (m) of a line passing through two points (x1, y1) and (x2, y2) is given by: \$m = (y2 - y1) / (x2 - x1)\$

Explanation: To find the slope (m) of a line passing through two points (x1, y1) and (x2, y2), use this formula:

\$m = (y2 - y1) / (x2 - x1)\$

Step 2a

Let’s plug in the coordinates of the given points (1, -2) and (4, -5): \$m = (-5 - (-2)) / (4 - 1)\$ then \$m = (-5 + 2) / 3 \$ m = -1.

Explanation: To find the coordinates of the given points, (1, -2) and (4, -5), we can input them into the equation and determine that the slope is -1.

Step 3a

In this step, Use the point-slope form. Now that we have the slope (m = -1) and one point (1, -2), we can write the equation of the line: y − y1 = m(x − x1)

⇒y - (-2) = -1(x - 1)

⇒ y + 2 = -1 (x) + 1

⇒ y = -1 (x) + 1 - 2

⇒ y = -1 (x) - 1

Explanation: To proceed, apply the point-slope form. With the slope (m = -1) and one point (1, -2), we can formulate the equation of the line as follows: y − y1 = m(x − x1). Therefore, substituting the values, we get y - (-2) = -1(x - 1).

Step 4a

Let’s move on to the next step, where we will compare the equation with slope-intercept form (y = mx + b), where "b" represents the y-intercept.

Here’s the simplified equation is : y = -1 (x) - 1

After further simplification, we get: y = - 1(x) + (-1)

From the above equation we get y-intercept(b) = -1

Explanation: Convert the equation to slope - intercept form, y = mx + b, where "b" is the y - intercept. The simplified equation is y = - 1(x) + (-1).

Step 5a

So, the equation of the line passing through the points (1, -2) and (4, -5) is y = -x - 1.

Explanation: The equation for the line that passes through the coordinates (1, -2) and (4, -5) is y = -x - 1.


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