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What is the equation in slope-intercept form of the line that passes through the points (−12, −4) and (4, 8)?


A. y = −43 − 20
A. , y = −43 − 20

B. y = 43 − 12
B. , y = 43 − 12

C. y = −0.75 − 13
C. , y = −0.75 − 13

D. y = 0.75x +5
D. , y = 0.75x +5

Respuesta :

jacob193

Answer:

Choice D. [tex]y = 0.75\, x + 5[/tex].

Step-by-step explanation:

The general equation for the slope-intercept form of a line in a cartesian plane is [tex]y = m\, x + b[/tex], where:

  • [tex]m[/tex] is the slope of the line, and
  • [tex]b[/tex] is the [tex]y[/tex]-intercept of the line. (The [tex]y\![/tex]-intercept of a line in a cartesian plane is the [tex]y\!\![/tex]-coordinate of the point where the line intersects the [tex]\! y \![/tex]-axis.)

Start by finding the value of [tex]m[/tex]. The slope of a line is equal to its rise-over-run. For the two points in this question:

  • The "rise" is the [tex]y[/tex]-coordinate of the first point minus that of the second: [tex]\text{rise} = (-4) - 8 = -12[/tex].
  • The "run" is the [tex]x[/tex]-coordinate of the first point minus that of the second. The order of these two points should stay the same: [tex]\text{run} = (-12) - 4 = -16[/tex].

Calculate the slope of this line:

[tex]\displaystyle m = \text{slope} = \frac{\text{rise}}{\text{run}} = \frac{-12}{-16} = 0.75[/tex].

The equation of the line becomes:

[tex]y = \underbrace{0.75}_{m}\, x + b[/tex].

Substitute the coordinates of either of the two points to find [tex]b[/tex]. For example, for the first point [tex](12, -4)[/tex], substitute in the following:

  • [tex]x = -12[/tex], and
  • [tex]y = -4[/tex].

The equation becomes:

[tex]-4 = 0.75 \times (-12) + b[/tex].

Solve for the value of [tex]b[/tex]:

[tex]b = 5[/tex].

Hence, the slope-intercept form of this line shall be:

[tex]y = 0.75\, x + 5[/tex].

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