Questions: Find an equation of the line that passes through the two given points. If possible, write the equation in slope-intercept form. Check that the graph of the equation contains the given points.
(-4,-20) and (6,20)
Transcript text: Find an equation of the line that passes through the two given points. If possible, write the equation in slope-intercep form. Check that the graph of the equation contains the given points.
\[
(-4,-20) \text { and }(6,20)
\]
Solution
Solution Steps
To find the equation of the line that passes through the two given points, we need to:
Calculate the slope (m) using the formula \( m = \frac{y_2 - y_1}{x_2 - x_1} \).
Use the slope and one of the points to find the y-intercept (b) using the formula \( y = mx + b \).
Write the equation in slope-intercept form \( y = mx + b \).
Verify that the equation contains the given points by substituting the points into the equation.
Step 1: Calculate the Slope
Given points \((-4, -20)\) and \( (6, 20) \), we calculate the slope \( m \) using the formula:
\[
m = \frac{y_2 - y_1}{x_2 - x_1}
\]
Substituting the given points:
\[
m = \frac{20 - (-20)}{6 - (-4)} = \frac{40}{10} = 4.0
\]
Step 2: Calculate the Y-Intercept
Using the slope \( m = 4.0 \) and one of the points, say \((-4, -20)\), we find the y-intercept \( b \) using the formula:
\[
y = mx + b
\]
Substituting the values:
\[
-20 = 4.0 \cdot (-4) + b \implies -20 = -16 + b \implies b = -4.0
\]
Step 3: Write the Equation in Slope-Intercept Form
Using the calculated slope \( m = 4.0 \) and y-intercept \( b = -4.0 \), the equation of the line is:
\[
y = 4.0x - 4.0
\]
Step 4: Verify the Equation with Given Points
We verify that the equation \( y = 4.0x - 4.0 \) contains the given points:
For \((-4, -20)\):
\[
y = 4.0(-4) - 4.0 = -16 - 4 = -20 \quad \text{(True)}
\]
For \( (6, 20) \):
\[
y = 4.0(6) - 4.0 = 24 - 4 = 20 \quad \text{(True)}
\]