F4 Equation of Staright Lines

Let L(1) : y = mx + c , L(2) : y = ( m" )x + c"

L(1) has a positive x-intercept,
i.e. m < 0
L(2) has a negative x-intercept,
i.e. m" > 0

L(1) is perpendicular to L(2),
i.e. ( m )( m" ) = - 1
m = - 1 / m"

So, L(1) : y = ( - 1 / m" )x + c and L(2) : y = ( m" )x + c"
One of the possible equations of two straight lines :
L(1) : y = ( - 1 / 2 )x + 1
L(2) : y = ( 2 )x + 1