Which of the following equations are equations of a direct variation? Choose all that apply. (a) x=−2y
(b) x+2y=12
(c) 3x−2y=0
(d) 5x^2+y=0
(e) y =0.3x +1.6
(f) y−2=x

For a short time after a wave is created by wind , the height of the wave can be modeled using y= a sin 2pi(t) / t where a is the amplitude and t is the period of the wave in seconds. how many times over the first 5 seconds does the graph predict the wave to be 2 feet high?