Need help #1. The answer is shown, but I don’t know how to get to the answer. Please teach and show steps.

B

Step-by-step explanation:

We are given that x and y are functions of time t such that x and y is a constant. So, we can write the following equation:

The rate of change of x and the rate of change of y with respect to time t is simply dx/dt and dy/dt, respectively. So, we will differentiate both sides with respect to t:

Remember that the derivative of a constant is always 0. Therefore:

And by subtracting dy/dt from both sides, we acquire:

Hence, our answer is B.

Let x and y be functions of time t such that the sum of x and y is constant.

b

step-by-step explanation:

the word superfluous means unnecessary

its 50 miles away from the starting point