You would use the slope-intercept form y-y1=m(x-x1)
In this case, -7 would be x1, and -4 would be y1.
y-(-7)=m(x-(-4))
which would turn to y+7=m(x+4)
In order to be perpendicular, the slope, m, would have to be the negative reciprocal of 1/2, which is -2.
y+7=-2(x+4)
y+7=-2x-8
-7 -7
y=-2x-15
