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Help Please! I dont understand these questions!
Directions: Write the equation of the line in point-slope form, then convert that equation to slope-intercept form. Show your work!

1. Write the equation of the line that is parallel to y = 2x + 4 and passes through the point (-4, -1).

2. Write the equation of the line that is parallel to y = ⅓x - 3 and passes through the point (3, -1).

3. Write the equation of the line that is perpendicular to y = ¾x - 1 and passes through the point (3, -3).

4. Write the equation of the line that is perpendicular to y = -x - 5 and passes through the point (7, 3).


Sagot :

The point-slope form of the equation of line it's y - y₁ = m(x - x₁), where m is the slope and (x₁, y₁) is the point the line passing through.

The slope-intercept form of the equation of line it's y = mx + b, where m is the slope and b is the y-intercept of the line.

1. Write the equation of the line that is parallel to y = 2x + 4 and passes through the point (-4, -1).

y=m₁x+b₁   ║   y=m₂x+b₂   ⇔    m₁ = m₂

{Two lines are parallel if  their slopes are equal}

y = 2x + 4  ⇒   m₁ = 2    ⇒    m₂ = 2

(-4, -1)  ⇒  x₁ = -4,  y₁ = -1

point-slope form:

y - (-1) = 2(x - (-4))

y + 1 = 2(x + 4)

y + 1 = 2x + 8               {subtact 1 from both sides}

y = 2x + 7         ←    slope-intercept form

2. Write the equation of the line that is parallel to y = ⅓x - 3 and passes through the point (3, -1).

y = ⅓x - 3  ⇒   m₁ =  ⅓    ⇒    m₂ =  ⅓

(3, -1)  ⇒  x₁ = 3,  y₁ = -1

point-slope form:

y - (-1) = ⅓(x - 3)

y + 1 = ⅓x - 1           {subtact 1 from both sides}

y = ⅓x - 2         ←    slope-intercept form

3. Write the equation of the line that is perpendicular to y = ¾x - 1 and passes through the point (3, -3).

y=m₁x+b₁   ⊥   y=m₂x+b₂   ⇔    m₁×m₂ = -1

{Two lines are perpendicular if the product of theirs slopes is equal -1}

y = ¾x - 1   ⇒   m₁ = ¾  

¾×m₂ = -1        ⇒    m₂ = -⁴/₃

(3, -3)  ⇒  x₁ = 3,  y₁ = -3

point-slope form:

y - (-3) =  -⁴/₃(x - 3)

y + 3 = -⁴/₃x + 4           {subtact 3 from both sides}

y = -⁴/₃x + 1         ←    slope-intercept form

4. Write the equation of the line that is perpendicular to y = -x - 5 and passes through the point (7, 3).

y = - x - 5   ⇒   m₁ = -1  

-1×m₂ = -1        ⇒    m₂ = 1

(7, 3)  ⇒  x₁ = 7,  y₁ = 3

point-slope form:

y - 3 =  -1(x - 7)

y - 3 = - x + 7           {add 3 to both sides}

y = - x + 10         ←    slope-intercept form