Question

What is the equation of a line through the points (0,9) and (3,0)

Answer 1

The slope of the line is 9-0 / 0-3 = -3

the y intercept is at y= 9

y = mx + b

so here we have


y = -3x + 9 answer

Answer 2

y = kx + b

(0,9) x = 0; y = 9
y = kx + b
9 = k*0 + b
9 = b

(3,0) x = 3; y = 0
y = kx + 9
0 = k*3 + 9
-9 = 3k
k = -3

The equation of a line y = -3x + 9