The equations are and 

The line equation in slope-intercept form is .

where  is the slope and  is the -intercept.

Find the slope. \ \

Here, the slope is .

Find the slope. \ \

.

Here, the slope is .

Slope of the first equation is .

Slope of the second equation is .

If two lines are parallel, their slopes must be equal. (Or)

If two lines are said to be perpendicular,the product of their slopes is equal to .

Here, the product of two slopes is equal to , thus the lines are perpendicular.

The lines are perpendicular.