Question

Find the equation of the line passing through the 2 points (9,-1) (0,-8)

Answer 1

Answer: y=(7/9)x-8

Explanation:

y=mx+b line equation

m= y¹-y²/x¹-x²

m= (-1)-(-8)/9-0

m= -1+8/9

m=7/9

y=(7/9)x+b

To find b put the value of point (9-1) in the equation

-1= (7/9)(9)+b

-1= 7+b

-1-7=b

-8=b

Answer 2

y =
`(7)/(9)` x - 8

Explanation:

The equation of a line in slope- intercept form is

y = mx + c ( m is the slope and c the y- intercept )

Calculate m using the slope formula

m = (y₂ - y₁ ) / (x₂ - x₁ )

with (x₁, y₁ ) = (9, - 1) and (x₂, y₂ ) = (0, - 8)

m =
`(-8+1)/(0-9)` =
`(-7)/(-9)` =
`(7)/(9)`

Note the line crosses the y- axis at (0, - 8) ⇒ c = - 8

y =
`(7)/(9)` x - 8 ← equation of line