Which can be the first step in finding the equation of the line that passes through the points (5, negative 4) and (negative 1, 8) in slope-intercept form?

Calculate StartFraction 8 minus (negative 4) Over negative 1 minus 5 EndFraction = StartFraction 12 Over negative 6 EndFraction = negative 2..
Calculate StartFraction negative 1 minus 5 Over 8 minus (negative 4) EndFraction = StartFraction negative 6 Over 12 EndFraction = negative one-half..
Find that the point at which the line intersects with the line y = 0 is (3, 0).
Find that the point at which the line intersects with the line x = y is (2, 2).

1 answer

To find the equation of the line that passes through the points (5, -4) and (-1, 8), the first step is to calculate the slope of the line using the two given points. The formula for the slope \( m \) between two points \( (x_1, y_1) \) and \( (x_2, y_2) \) is:

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

Let’s assign the points:

  • Point 1: \( (x_1, y_1) = (5, -4) \)
  • Point 2: \( (x_2, y_2) = (-1, 8) \)

Substituting the values into the formula, we have:

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

Calculating this gives:

\[ m = \frac{8 + 4}{-1 - 5} = \frac{12}{-6} = -2 \]

So the slope \( m = -2 \).

Now, the next step would be to use the point-slope form of the linear equation, which is given by:

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

You can use either of the points, but let’s use \( (5, -4) \):

\[ y - (-4) = -2(x - 5) \]

Simplifying this, we get:

\[ y + 4 = -2(x - 5) \] \[ y + 4 = -2x + 10 \] \[ y = -2x + 10 - 4 \] \[ y = -2x + 6 \]

Thus, the equation of the line in slope-intercept form is:

\[ y = -2x + 6 \]

From here, you could check specific points regarding their intersections with other lines, but calculating the slope was the essential first step in this problem.