# How do you find the slope of a line parallel to 3x`+y=15 ?

Jun 15, 2015

$m = - 3$

#### Explanation:

Explicit the equation:

$y = - 3 x + 15$

Since every parallel line is of the form $y = - 3 x + q$, we have its slope is always $m = - 3$

(To prove this, you might consider an $m$ such that $- 3 x + 15 - m x - q = 0$ has no solution for every $q \ne 15$, it is pretty obvious you have to consider the only m such that -3-m=0, or you will have a linear equation which has always a solution)