Formula for a Line

Question

Write a formula for a line that passes through the point (x,y)=(-4,8) and has the following slopes.

(a) 1.24
(b) 0
(c) undefined

Answer 1

a) y = 1.24 x + b

 

8 =1.24(-4) +b

 

8=-4.96 +b

 

8+4.96= b

 

b=12.96

 

y=1.24x +12.96

 

 

 

 

b)0

 

slope of horizontal lines are 0

 

y =  8

 

 

c) undefined

 

slope of vertical lines are undefined

 

x=-4

 

Answer 2

Use the point-slope form for the equation of a line.

y - y₁ = m(x - x₁)

(a) y - 8 = 1.24(x + 4)

y - 8 = 1.24x + 4.96

y = 1.24x + 12.96

 

(b) A line with a slope of 0 is a horizontal line. So, y = 8.

 

(c)  A line with an undefined slope is a vertical line. So, x = -4.