Question 30202
x + y = 5 --> y = -x + 5
x - y = 1 --> y = x - 1


Written in this form, the coefficient of x is the gradient... we have -1 and +1. They are not parallel.


If (grad1)*(grad2) = -1 then the lines are perpendicular.


-1*1 is -1... so the 2 lines are perpendicular.


jon.