What is the standard form equation of the line shown below?

Graph of a line going through negative 2, 3 and 1, negative 3

a. y + 3 = −2(x − 1)
b. y = −2x − 1
c. 2x + y = −1
d. −2x − y = 1

Respuesta :

gmany

The point-slope form:

[tex]y-y_1=m(x-x_1)[/tex]

m - slope

The formula of a slope:

[tex]m=\dfrac{y_2-y_1}{x_2-x_1}[/tex]

We have the points (-2, 3) and (1, -3). Substitute:

[tex]m=\dfrac{-3-3}{1-(-2)}=\dfrac{-6}{3}=-2\\\\y-(-3)=-2(x-1)\\\\y+3=-2(x-1)[/tex]

The standard form: Ax + By = C. Convert:

[tex]y+3=-2(x-1)[/tex]      use distributive property

[tex]y+3=-2x+2[/tex]         subtract 3 from both sides

[tex]y=-2x-1[/tex]       add 2x to both sides

[tex]\boxed{2x+y=-1}\to\boxed{c.}[/tex]

Answer:

b

Step-by-step explanation:

You can determine the gradient from the two points (-2, 3) and (1, -3). The gradient of a straight line is:

[tex]m=(y_2-y_1)/(x_2-x_1)[/tex]

[tex]m=(-3-3)/(1-(-2))=-6/3=-2[/tex]

The equation for a straight line is:

[tex]y=m\cdot{x}+c[/tex]

c is the y-intercept when x=0. We can substitute any point into the equation. Lets use point 1 and solve for c .

[tex]3=-2\cdot{-2}+c[/tex]

[tex]c=-1[/tex]

The equation is:

[tex]y=-2\cdot{x}-1[/tex]

The answer is b