Question 76628
Determine whether the lines are parallel, perpendicular, or neither.
1) {{{y - 3x = 10}}} and 
2) {{{3y + x = -5}}}
First, put your equations into the slope-intercept form: y = mx + b
1) {{{y = 3x + 10}}} and
2) {{{y = (-1/3)x - 5/3}}}
Notice that the slope (m) in equation 1) is 3 and the slope (m) in equation 2 is -1/3
Recall that perpendicular lines have slopes that are the negative reciprocal of each other.
So, equation 1) has a slope of 3 while equation 2) has a slope of -1/3 which is the negative reciprocal of 3.  The lines are, therefore, perpendicular.