Question

Find the solution of the differential equation that satisfies the given initial condition.

dy/dx = x/y, y(0) = −3

Answer 1

y=-sqrt(x^2+9)

Explanation:

This problem can be solved with the help of separating the variables.

dy/dx=x/y

Multiply both sides by y

y dy/dx=x

Multiply both sides by dx

y dy=x dx

Integrate

y^2/2=x^2/2+c

Let's find c using the condition y(0)=-3.

(-3)^2/2=(0)^2/2+c

9/2=0+c

9/2=c.

The equation is y^2/2=x^2/2+9/2.

Let's make this a bit prettier multiplying both sides by 2:

y^2=x^2+9

Taking square root of both sides gives:

y=+/- sqrt(x^2+9)

Since we want y(0)=-3, then we will choose

y=-sqrt(x^2+9).