Question 135020
{{{y = mx + b}}} is the general form of a straight line equation where
{{{m}}}= slope. You are given 2 points (-3,0) and (0,-3) on a line
For 1st point, substitute for {{{y}}} and {{{x}}}
{{{0 = m*(-3) + b}}}
{{{0 = -3m + b}}}
{{{m = b/3}}}
And the same for the 2nd point
{{{-3 = m*0 + b}}}
{{{b = -3}}}
and
{{{m = b/3}}}
{{{m = -3/3}}}
{{{m = -1}}}
So, the equation of the line through (-3,0) and (0,-3) is
{{{y = -x - 3}}}
A line perpendicular to this line will have slope = {{{-(1/m) = -(1/(-1))}}}  so, slope = {{{1}}}
What is the equation of the line through the origin with slope = 1?
In the formula {{{y = mx + b}}}, {{{b}}} is the y-intercept, and a line
through the origin has {{{b = 0}}}
{{{y = 1*x + 0}}} or
{{{y = x}}} is the answer