perpendicular has slope that multiplies to -1
the slope for ax+by=c is -a/b
-1x+2y=4
slope=-(-1)/2=1/2
1/2 times what=-1?
-2
y=mx+b
m=slope
we need slope is -2
y=-2x+b
find b
given
(-2,1)
(x,y)
x=-2 and y=1 is a solution
1=-2(-2)+b
1=4+b
mius 4 both sides
-3=b
y=-2x-3 is equation
first one
