Answer:
B
Step-by-step explanation:
We are given that <em>x</em> and <em>y</em> are functions of time <em>t</em> such that <em>x</em> and <em>y</em> is a constant. So, we can write the following equation:
The rate of change of <em>x</em> and the rate of change of <em>y</em> with respect to time <em>t</em> is simply dx/dt and dy/dt, respectively. So, we will differentiate both sides with respect to <em>t: </em>
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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.