## Periodic solutions to a kind of delay Duffing equation.(Chinese. English summary)Zbl 0921.34066

Summary: The Duffing equation $$ax''+bx+g(x(t-\tau))=p(t)$$ is considered, using the theory of coincidence degree. A sufficient condition for the existence of at least one $$2\pi$$-periodic solution is obtained.

### MSC:

 34K13 Periodic solutions to functional-differential equations 34C25 Periodic solutions to ordinary differential equations

### Keywords:

delay Duffing equation; existence