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Find the solution to the differential equation below, subject to the given initial condition.

dB/dt + 2B = 50 B(1) = 60
B(t) =

User Atos
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1 Answer

4 votes

Final answer:

To solve the differential equation dB/dt + 2B = 50, we can separate the variables and integrate both sides. Applying the initial condition B(1) = 60, we can solve for the constant of integration and find the solution to be B = 25 ± e^(-2(t - 1 - (1 + ln(±70) / 2))) / 2.

Step-by-step explanation:

To solve the differential equation dB/dt + 2B = 50, we can first rewrite it as dB = (50 - 2B)dt. Next, we can separate the variables by dividing both sides by (50 - 2B), giving us dB / (50 - 2B) = dt. We can then integrate both sides:

∫(1 / (50 - 2B)) dB = ∫dt

To evaluate the integrals, we can use a substitution. Let u = 50 - 2B. Then du = -2dB and dt = -du / 2. Substituting these back into the equation, we get:

∫(1 / u) (-1/2) du = ∫dt

By evaluating the integrals, we have -1/2 ln|u| = t + C, where C is the constant of integration.

Now, we can substitute back in for u: -1/2 ln|50 - 2B| = t + C. Next, we can solve for B:

ln|50 - 2B| = -2(t + C)

|50 - 2B| = e^(-2(t + C))

50 - 2B = ±e^(-2(t + C))

Solving for B, we get B = 25 ± (e^(-2(t + C)) / 2)

Now, we can apply the initial condition B(1) = 60. Since t = 1, we have B = 60. Plugging that in, we can solve for C:

60 = 25 ± (e^(-2(1 + C)) / 2)

Subtracting 25 and multiplying both sides by 2:

70 = ±e^(-2(1 + C))

e^(-2(1 + C)) = ±70

-2(1 + C) = ln(±70)

1 + C = -ln(±70) / 2

C = -1 - ln(±70) / 2

Plugging this value of C back into our earlier equation for B, we get:

B = 25 ± e^(-2(t - 1 - (1 + ln(±70) / 2))) / 2

Therefore, the solution to the differential equation with the given initial condition is B = 25 ± e^(-2(t - 1 - (1 + ln(±70) / 2))) / 2.

User Chris Cashwell
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