Question

two roads intersect at right angles. An observer stands on the road 12 meters south of the intersection and watches a cyclist travelling eastwards at 8 meters/sec. At what speed is the cyclist moving away from the observer 2 seconds after he passes through the intersection

Answer 1

can someone please answer this

Answer 2

the question asks for dR/dt.
differentiate R with respect to time... treat x as a function of time, because it changes with time.

dx/dt = 8 m/s
find x when t=2
plug these values into the expression you found for dR/dt