Which, if any, are perpendicular

A. y=x
B. y= -5x + 4
C. y= 2/3x + 1
D. y= -0.1x + 6
E. y= 3x - 5
F. y= -x - 1
G. 2x - 3y = 6
H. 6x + 3y = 9

Solve G and H in terms of y
G. y=2x/3-2
H. y=-2x+3

A is perp. to F, because the slopes are 1 and -1, which are negative inverses to each other. However, maybe I'm missing something, but that's the only one I see

dunno