9x+y=-7 & x-9y=7

Question

are they parall or perpendicular 

Answer 1

if you solve for y (i.e. slope-intercept form), then you can see if it's parallel or perpendicular

 

for parallel lines, both equations should have identical slope
for perpendicular lines, the slope should be reciprocal and different sign

 

9x+y=-7

 

y = -9x -7  slope is -9

 

x-9y=7

 

-9y = -x + 7

 

y = 1x/9 - 7/9   slope is 1/9

 

 

these equations are perpendicular