Q. What is the particular solution to the differential equation dxdy=1−2x3+y with the initial condition y(0)=0 ?
Separate variables: Separate the variables in the differential equation.We want to get all the y terms on one side and all the x terms on the other side. This can be done by multiplying both sides by (1−2x)dx and dividing by (3+y).So we get (1−2x)dx=3+ydy.
Integrate both sides: Integrate both sides of the equation.We integrate the left side with respect to x and the right side with respect to y.∫(1−2x)dx=∫3+ydy
Perform integration: Perform the integration.The left side becomes x−x2+C1, where C1 is the constant of integration.The right side becomes ln∣3+y∣+C2, where C2 is the constant of integration.So we have x−x2+C1=ln∣3+y∣+C2.
Combine constants: Combine the constants of integration.Since C1 and C2 are both constants, we can combine them into a single constant, which we'll call C.So we have x−x2=ln∣3+y∣+C.
Apply initial condition: Apply the initial condition to find C. We are given that y(0)=0, so we plug in x=0 and y=0 into the equation. 0−02=ln∣3+0∣+C This simplifies to 0=ln(3)+C. So C=−ln(3).
Write particular solution: Write the particular solution with the value of C. Substitute C back into the equation to get the particular solution. x−x2=ln∣3+y∣−ln(3)
Simplify equation: Simplify the equation by using properties of logarithms.We can use the property of logarithms that ln(a)−ln(b)=ln(ba) to combine the logarithms on the right side.x−x2=ln(∣3+y∣/3)
Remove absolute value: Remove the absolute value.Since ln(a) is only defined for a > 0, and 3+y > 0 for the solution to exist, we can remove the absolute value.x−x2=ln((3+y)/3)
Exponentiate to solve: Exponentiate both sides to solve for y. Raise e to the power of both sides to get rid of the natural logarithm. ex−x2=33+y
Solve for y: Solve for y.Multiply both sides by 3 to isolate y.3e(x−x2)=3+yy=3e(x−x2)−3
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