SOLUTION: A Bernoulli differential equation is one of the form dy/dx+P(x)y=Q(x)y^n. Observe that, if n=0 or 1, the Bernoulli equation is linear. For other values of n, the substitution

Algebra ->  Expressions-with-variables -> SOLUTION: A Bernoulli differential equation is one of the form dy/dx+P(x)y=Q(x)y^n. Observe that, if n=0 or 1, the Bernoulli equation is linear. For other values of n, the substitution       Log On


   



Question 1184077: A Bernoulli differential equation is one of the form
dy/dx+P(x)y=Q(x)y^n.
Observe that, if n=0 or 1, the Bernoulli equation is linear. For other values of n, the substitution u=y1−n transforms the Bernoulli equation into the linear equation
du/dx+(1−n)P(x)u=(1−n)Q(x).
Use an appropriate substitution to solve the equation
y′−(7/x)y=(y^4/x^5), and find the solution that satisfies y(1)=1.
y(x)= ?

Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
Let u+=+y%5E%281-4%29+=+y%5E%28-3%29. Substituting this into the original D.E. and simplifying, you get

%22u%27%22+%2B+%2821%2Fx%29u+=+-3%2Fx%5E5.

The integrating factor is e%5E%2821int%28dx%2Fx%29%29+=+x%5E21.
After multiplying D.E. with the integrating factor and integrating,
you get

ux%5E21+=+%28-3%2F17%29x%5E17+%2B+C. ===> y%5E%28-3%29x%5E21+=+%28-3%2F17%29x%5E17+%2B+C, or 1%2Fy%5E3+=+-3%2F%2817x%5E4%29+%2B+C%2Fx%5E21.

solving for C when y(1) = 1 gives C+=+20%2F17, so that

1%2Fy%5E3+=+-3%2F%2817x%5E4%29+%2B+20%2F%2817x%5E21%29.