Let x and y be functions of time t such that the sum of x and twice y is constant. Which of the following equations describes the relationship between the rate of change of with respect to time and the rate of
change of with respect to time?
A) dx/dt=2dy/dt
B) dx/dt=-2dy/dt
C) 2dx/dt+dy/dt=0
D) dx/dt + 2dy/dt=K, where K is a function of t