Question

A line passes through the points (1. 4) and (3.-4). Which is the equation of the line?

O
y=-4x+8
y=-2x + 8
0 - - 4x + 2
o y= 2x+2

Answer 1

Slope-intercept form: y = mx + b

(m is the slope, b is the y-intercept or the y value when x = 0 --> (0, y) or the point where the line crosses through the y-axis)

To find the slope(m), use the slope formula:

`m=(y_2-y_1)/(x_2-x_1)` And plug in the two points on the line

(1, 4) = (x₁, y₁)

(3, -4) = (x₂, y₂)

`m=(y_2-y_1)/(x_2-x_1)`

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

`m=(-8)/(2)` Simplify the fraction

m = -4

Now that you know the slope, substitute/plug it into the equation.

y = mx + b

y = -4x + b To find b, plug in either of the points into the equation, it doesn't matter which, the isolate/get the variable "b" by itself. I will use (1, 4)

4 = -4(1) + b Add 4 on both sides to get "b" by itself

4 + 4 = -4 + 4 + b

8 = b

y = -4x + 8 Your answer is the 1st option