Q. dxdy=3y, and y=2 when x=1.Solve the equation.Choose 1 answer:(A) y=e3x−6(B) y=2e3x+1(C) y=2e3x+3(D) y=2e3x−3
Recognize First-Order Linear Equation: Recognize that the given differential equation dxdy=3y is a first-order linear differential equation that can be solved using separation of variables.
Separate Variables: Separate the variables by dividing both sides by y and multiplying both sides by dx to get y1dy = 3dx.
Integrate Both Sides: Integrate both sides of the equation. The integral of (1/y)dy is ln∣y∣, and the integral of 3dx is 3x. So we have ln∣y∣=3x+C, where C is the constant of integration.
Solve for y: Solve for y by exponentiating both sides to get rid of the natural logarithm. This gives us ∣y∣=e(3x+C). Since y is positive (y=2 when x=1), we can drop the absolute value to get y=e(3x+C).
Use Initial Condition: Use the initial condition y=2 when x=1 to find the value of C. Substituting these values into y=e3x+C gives us 2=e3⋅1+C, which simplifies to 2=e3+C.
Solve for C: Solve for C by taking the natural logarithm of both sides. We get ln(2)=3+C, which simplifies to C=ln(2)−3.
Substitute C Value: Substitute the value of C back into the equation y=e3x+C to get the particular solution. This gives us y=e3x+ln(2)−3.
Simplify Equation: Simplify the equation using properties of exponents. We know that eln(2)=2, so we can rewrite the equation as y=2e3x−3.
Compare with Choices: Compare the simplified equation with the answer choices to find the correct one. The equation y=2e3x−3 matches with choice (D) y=2e3x−3.
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