# CALCULUS

Let y(t) denote the mass of a radioactive substance at time t.t. Suppose this substance obeys the equation
y′(t)=−14y(t).

Assume that, initially, the mass of the substance is y(0)=M>0. At what time does half of the mass remain? (Round your answer to 3 decimal places).

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1. this is just like the other one. You already know about radioactive decay, and how it is an exponential function, right?

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2. Yes but I'm not sure what the m>0 is for

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3. surely the initial mass is positive. Kind of makes things more real.

Looking at the original equation, if y(0) < 0, we have exponential growth, not decay.

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