Question 933896
we are given
2x +y =-9
-4y =-2x + 7 
next put each equation in standard form, y = mx + b
y = -2x -9
y = x/2 - 7/4
the slope of these two lines is the negative reciprocal of the other, the lines are perpendicular
here is their graph
{{{ graph( 300, 200, -10, 10, -10, 10, -2x-9, x/2 - 7/4) }}}