Me solve this: a bicyclist in the tour de france crests a mountain pass as he moves at 18 km/h. at the bottom, 4.0 km farther, his speed is 75 km/h. what was his average acceleration (in m/s square) while riding down the mountain?

First we have to convert:
75 km / h ( * 3.6 ) = 270 m/s
18 m/s = 64.8 m/s
d = v i · t + 1/2 a · t²
v = v i + a t

4000 = 64.8 · t + 1/2 a · t²
270 = 64.8 + a t
a = ( 270 - 64.8 ) / t
a = 205.2 / t
4000 = 64.8 t + 1/2 · ( 205.2 / t ) · t²
4000 = 64.8 t + 102.6 t
4000 = 167.4 t
t = 4000 : 167.4 = 23.89 s
a = 205.2 : 23.89 = 8.58 m/s²
His average acceleration was 8.58 m/s²

B. convex since the words are bigger

3is a crest4 is a trough 2 is the amplitude 1 is the wavelength