Step-by-step explanation:
The equation of motion for a frictionless roller coaster is given by: v2 = v02 + 2ay, where v0 is the initial velocity, a is the acceleration due to gravity (9.8 m/s2), and y is the height.
Plugging in the given values of v0, y0 and y1, we get: v2 = 92 + 2(9.8)(-2.6) = 77.88 m/s2.
Therefore, the speed of the roller coaster at the lowest point (y1) will be v = √77.88 m/s = 8.82 m/s.