Which graph represents the sequence: 80, -40, 20

 80/-40=-40/20=-2, 
the sequence: 80, -40, 20 is a geometric sequence
its general formula is Vn+1 = q Vn, where q= -2,
if we put Vn+1 = f(x)
               Vn = x 

so we have f(x)= -2x so the graph that represents the sequence is graph of linear equation

It is blindness and randomization