Using point-slope form, write the equation of the line that passes through (2, –1) and has a slope of –5.
(y+1)/(x-2) = -5/1
y+1= -5x +10
5x + y = 9 or y = -5x + 9
or
using y = mx + b
y = -5x + b , but (2,-1) lies on it, so
-1 = -5(2) + b
9 = b
y = -5x + 9
(personally, I usually use the first method, since in most cases, it allows me to avoid the use of fractions)