two lines are parallel if their slope is equal
equation of line is
y=mx+c
where m=slope
for y=2x-5
m=2
for -x+2y=-5
2y=-5+x
y=-5/2+x/2
m=1/2
lines are nor parallel becuase m (slope) is not equal
now we will test for perpendicularity
perpendicular lines have slopes that are reciprocal of each other
first line , m=2
second line, m=1/2
2 and 1/2 are reciprocals
therefore, the lines are perpendicular
