Question 74540
Solve each equation so that they are in the form y=mx+b
L1 : {{{ x – 7y = 21 }}}
{{{-7y = -x + 21 }}}
{{{ y = (1/7)x - 3 }}}
m = 1/7


L2 : {{{ 7x + y = 7 }}}
{{{ y = -7x +7 }}}
m=-7


since the slopes are opposite reciprocals of one another, the lines are perpendicular to one another.