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(dy)/(dt)=2y, and 
y=8 when 
t=0.
Solve the equation.
Choose 1 answer:
(A) 
y=e^(2t)
(B) 
y=2e^(8t)
(C) 
y=e^(8t)
(D) 
y=8e^(2t)

dydt=2y \frac{d y}{d t}=2 y , and y=8 y=8 when t=0 t=0 .\newlineSolve the equation.\newlineChoose 11 answer:\newline(A) y=e2t y=e^{2 t} \newline(B) y=2e8t y=2 e^{8 t} \newline(C) y=e8t y=e^{8 t} \newline(D) y=8e2t y=8 e^{2 t}

Full solution

Q. dydt=2y \frac{d y}{d t}=2 y , and y=8 y=8 when t=0 t=0 .\newlineSolve the equation.\newlineChoose 11 answer:\newline(A) y=e2t y=e^{2 t} \newline(B) y=2e8t y=2 e^{8 t} \newline(C) y=e8t y=e^{8 t} \newline(D) y=8e2t y=8 e^{2 t}
  1. Separation of Variables: The given differential equation is dydt=2y\frac{dy}{dt} = 2y. This is a first-order linear differential equation that can be solved using separation of variables. We will separate the variables yy and tt to integrate them separately.
  2. Integrating Separated Variables: We rewrite the equation to separate the variables: (1/y)dy=2dt(1/y)\,dy = 2\,dt. This allows us to integrate both sides with respect to their respective variables.
  3. Finding Constant of Integration: Integrating both sides, we get: (1y)dy=2dt\int(\frac{1}{y})dy = \int 2 dt. The integral of (1y)dy(\frac{1}{y})dy is lny\ln|y| and the integral of 2dt2 dt is 2t2t. So we have lny=2t+C\ln|y| = 2t + C, where CC is the constant of integration.
  4. Substitute Initial Condition: To find the constant of integration CC, we use the initial condition given: y=8y=8 when t=0t=0. Substituting these values into the equation lny=2t+C\ln|y| = 2t + C, we get ln8=2(0)+C\ln|8| = 2(0) + C. This simplifies to ln(8)=C\ln(8) = C.
  5. Final Solution: Now we have the constant CC, which is ln(8)\ln(8). We substitute this back into the equation lny=2t+C\ln|y| = 2t + C to get lny=2t+ln(8)\ln|y| = 2t + \ln(8).
  6. Final Solution: Now we have the constant CC, which is ln(8)\ln(8). We substitute this back into the equation lny=2t+C\ln|y| = 2t + C to get lny=2t+ln(8)\ln|y| = 2t + \ln(8).To solve for yy, we exponentiate both sides of the equation to get rid of the natural logarithm: elny=e2t+ln(8)e^{\ln|y|} = e^{2t + \ln(8)}. This simplifies to y=e2teln(8)|y| = e^{2t} \cdot e^{\ln(8)}.
  7. Final Solution: Now we have the constant CC, which is ln(8)\ln(8). We substitute this back into the equation lny=2t+C\ln|y| = 2t + C to get lny=2t+ln(8)\ln|y| = 2t + \ln(8).To solve for yy, we exponentiate both sides of the equation to get rid of the natural logarithm: elny=e2t+ln(8)e^{\ln|y|} = e^{2t + \ln(8)}. This simplifies to y=e2teln(8)|y| = e^{2t} \cdot e^{\ln(8)}.Since eln(8)e^{\ln(8)} is simply 88, we have y=8e2t|y| = 8e^{2t}. Because yy is positive (as given by the initial condition ln(8)\ln(8)11 when ln(8)\ln(8)22), we can drop the absolute value to get ln(8)\ln(8)33.

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