Question

Write a linear equation in point slope form for the line that goes through (-1, 1) and (1, -3)

Answer 1

see explanation

Explanation:

The equation of a line in point- slope form is

y - b = m(x - a)

where m is the slope and (a, b) a point on the line

Calculate m using the slope formula

m = (y₂ - y₁ ) / (x₂ - x₁ )

with (x₁, y₁ ) = (- 1, 1) and (x₂, y₂ ) = (1, - 3)

m =
`(-3-1)/(1+1)` =
`(-4)/(2)` = - 2

Using either of the 2 points as a point on the line, then

Using (- 1, 1)

y - 1 = - 2(x - (- 1)), that is

y - 1 = - 2(x + 1) ← in point- slope form

Answer 2

y - 1 = -2(x + 1).

Explanation:

The slope = (-3-1)/(1 - -1)

= -4 / 2

= -2.

In point slope form:

y - y1 = m(x - x1)

Using m = -2 and the point (-1, 1):

y - 1 = -2(x + 1).