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(dy)/(dx)=3y, and 
y=2 when 
x=1.
Solve the equation.
Choose 1 answer:
(A) 
y=e^(3x-6)
(B) 
y=2e^(3x+1)
(C) 
y=2e^(3x+3)
(D) 
y=2e^(3x-3)

dydx=3y \frac{d y}{d x}=3 y , and y=2 y=2 when x=1 x=1 .\newlineSolve the equation.\newlineChoose 11 answer:\newline(A) y=e3x6 y=e^{3 x-6} \newline(B) y=2e3x+1 y=2 e^{3 x+1} \newline(C) y=2e3x+3 y=2 e^{3 x+3} \newline(D) y=2e3x3 y=2 e^{3 x-3}

Full solution

Q. dydx=3y \frac{d y}{d x}=3 y , and y=2 y=2 when x=1 x=1 .\newlineSolve the equation.\newlineChoose 11 answer:\newline(A) y=e3x6 y=e^{3 x-6} \newline(B) y=2e3x+1 y=2 e^{3 x+1} \newline(C) y=2e3x+3 y=2 e^{3 x+3} \newline(D) y=2e3x3 y=2 e^{3 x-3}
  1. Recognize First-Order Linear Equation: Recognize that the given differential equation dydx=3y\frac{dy}{dx}=3y is a first-order linear differential equation that can be solved using separation of variables.
  2. Separate Variables: Separate the variables by dividing both sides by yy and multiplying both sides by dxdx to get 1y\frac{1}{y}dydy = 3dx3dx.
  3. Integrate Both Sides: Integrate both sides of the equation. The integral of (1/y)dy(1/y)\,dy is lny\ln|y|, and the integral of 3dx3\,dx is 3x3x. So we have lny=3x+C\ln|y| = 3x + C, where CC is the constant of integration.
  4. Solve for yy: Solve for yy by exponentiating both sides to get rid of the natural logarithm. This gives us y=e(3x+C)|y| = e^{(3x+C)}. Since yy is positive (y=2y=2 when x=1x=1), we can drop the absolute value to get y=e(3x+C)y = e^{(3x+C)}.
  5. Use Initial Condition: Use the initial condition y=2y=2 when x=1x=1 to find the value of CC. Substituting these values into y=e3x+Cy = e^{3x+C} gives us 2=e31+C2 = e^{3\cdot 1+C}, which simplifies to 2=e3+C2 = e^{3+C}.
  6. Solve for C: Solve for C by taking the natural logarithm of both sides. We get ln(2)=3+C\ln(2) = 3 + C, which simplifies to C=ln(2)3C = \ln(2) - 3.
  7. Substitute C Value: Substitute the value of CC back into the equation y=e3x+Cy = e^{3x+C} to get the particular solution. This gives us y=e3x+ln(2)3y = e^{3x + \ln(2) - 3}.
  8. Simplify Equation: Simplify the equation using properties of exponents. We know that eln(2)=2e^{\ln(2)} = 2, so we can rewrite the equation as y=2e3x3y = 2e^{3x - 3}.
  9. Compare with Choices: Compare the simplified equation with the answer choices to find the correct one. The equation y=2e3x3y = 2e^{3x - 3} matches with choice (D) y=2e3x3y=2e^{3x-3}.

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