A line passes through (2, –1) and (8, 4).

a. Write an equation for the line in point-slope form.
b. Rewrite the equation in standard form using integers.

1 answer

To start, we’ll find the slope of the line passing through the points (2, -1) and (8, 4).

Step 1: Calculate the slope (m)

The formula for the slope \( m \) between two points \( (x_1, y_1) \) and \( (x_2, y_2) \) is:

\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]

Plugging in our points \( (2, -1) \) and \( (8, 4) \):

\[ m = \frac{4 - (-1)}{8 - 2} = \frac{4 + 1}{8 - 2} = \frac{5}{6} \]

Step 2: Write the equation in point-slope form

The point-slope form of a line is given by:

\[ y - y_1 = m(x - x_1) \]

Using the point (2, -1) and the slope \( m = \frac{5}{6} \):

\[ y - (-1) = \frac{5}{6}(x - 2) \]

This simplifies to:

\[ y + 1 = \frac{5}{6}(x - 2) \]

Step 3: Rewrite the equation in standard form using integers

First, we can distribute \( \frac{5}{6} \):

\[ y + 1 = \frac{5}{6}x - \frac{5}{3} \]

Next, we’ll get rid of the fractions by multiplying every term by 6:

\[ 6(y + 1) = 6\left(\frac{5}{6}x - \frac{5}{3}\right) \]

This simplifies to:

\[ 6y + 6 = 5x - 10 \]

Next, we rearrange this into standard form \( Ax + By = C \):

\[ -5x + 6y + 16 = 0 \]

To have the \( A \) term positive, we can multiply through by -1:

\[ 5x - 6y = 16 \]

Thus, the final equations are:

a. Point-slope form:
\[ y + 1 = \frac{5}{6}(x - 2) \]

b. Standard form:
\[ 5x - 6y = 16 \]