Journal of Applied Mathematics

Volume 2013, Article ID 589483, 8 pages

http://dx.doi.org/10.1155/2013/589483

## Exact Number of Positive Solutions for a Class of Two-Point Boundary Value Problems

School of Mathematical Sciences, Shandong Normal University, Jinan 250014, China

Received 25 September 2013; Accepted 4 November 2013

Academic Editor: Yansheng Liu

Copyright © 2013 Yanmin Niu and Baoqiang Yan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

This paper considers the existence of positive solutions of the boundary value problems and , where and is a positive parameter. Using a time-map approach, we obtain the exact number of positive solutions in different cases.

#### 1. Introduction and Main Results

The study of multiplicity results to boundary value problem where is a positive parameter, is very interesting because of its applications. As we know, when , the boundary value problem where and are fixed given numbers and is a parameter, comes from the elliptic problem with , which was raised by Ambrosetti et al. in [1].

Under different assumptions on , there are many results for the above problems and elliptic equations (see [2–8]).

In [9, 10], Liu considered the case of and and gave the exact number of solutions and many interesting properties of the solutions.

Cheng [11] investigated the following two-point boundary value problem: where is a positive parameter and and got the exact number of positive solutions.

Now, in this paper we consider the more general case where is a positive parameter, , and .

Define , where satisfies

For and , let be given byThe main results of this paper are as follows.

Theorem 1. *If , (5) has exactly one positive solution for any .*

Theorem 2. *If , (5) has exactly one positive solution for and none for .*

Theorem 3. *If , (5) has exactly one positive solution for and none for .*

Theorem 4. *If , (5) has exactly one positive solution for and none for . *

Theorem 5. *Assume that . Define
**
where and . One has the following.*(1)*If , (5) has exactly one positive solution for and none for .*(2)*If , there exists such that (5) has exactly two positive solutions for , exactly one for or , and none for . *

#### 2. The Proofs of Theorems 1–4

We assume throughout this section that and Denote that , where is given by (6). For and , let Define a function as It is clear that . Now we claim that for and if and only if .

Let and ; then . Immediately, we get that . In order to judge the sign of , we just judge the sign of . Since , , and , we can get the following two results.(1)For , the function has a stable point . When , we have , and when , we have .(2)For , we have on . Combining and with the above two results, we obtain the monotony of .(3)For , the function has a stable point on . When , we have and when , we have .(4)For , we have that on .(5)For or , we have that on .Then from , we infer that for .

We consider the integration . It is clear that is a flaw point. Since on , we consider the integration .

Using Lagrange theorem, we obtain that where are constants.

The following Lemma 6 is listed to show that to study the number of positive solutions of (5) is equivalent to study the shape of the map on . Lemmas 7–9 show some properties of on .

Lemma 6. *Let be the unique solution of the problem
**
where . One has the following.*(1)*If and is a positive solution of (5), , , and for .*(2)*If and , is a positive solution of (5) with .*

*Proof. *(1) Assume that and is a positive solution of (5). Let satisfy . It follows from that
This implies that and if . And combine to obtain
Then, we have that
It follows that
From (19) and we have that . With (17) and (18) we obtain the result (1) of this theorem.

(2) Since and is a positive solution of the boundary value problem
we have that is a positive solution of (5).

Lemma 7. * is differentiable on , and
**
where
*

*Proof. *Equation (21) can be obtained by (11), immediately. From
we have that
It follows from (21) that is differentiable on and (22) is true.

Lemma 8. *
Consider the following:**
where is given by (7).*

*Proof. *From
and the Lebesgue theorem, we have that
On the other hand, from , we can obtain that
This completes the proof of Lemma 8.

Lemma 9. *
Consider the following:*

*Proof. *From
we have thatFrom Lemma 7 and the Lebesgue theorem, we can obtain the results of this lemma.

In the following section, we give the proofs of Theorems 1–5. For convenience, we denote that Hence from Lemma 7, we have that

*Proof of Theorem 1. *From , we obtain that
for , . Thus for . By Lemmas 6, 8, and 9, we have the results of this theorem.

*Proof of Theorem 2. *From , (33), and (34), we have that for . It follows from Lemmas 6, 8, and 9 that the results of Theorem 2 hold.

*Proof of Theorem 3. *Conditions and imply that . With (33), we obtain that
for , , which means that for . Thus by Lemmas 6, 8, and 9, we have the results of this theorem.

*Proof of Theorem 4. *From and (33), we have that
for , . Hence for . By Lemmas 6, 8, and 9, we have the results of this theorem.

#### 3. The Proof of Theorem 5

In this section we always assume that . Denote that where , , and are given by (10), (6), and

*Remark 10. *From , (6), and (41), it is obvious that , , and .

Lemma 11. *For and ,
*

*Proof. *Let
Condition implies that
With and (44), we have that for .

It follows that
Combining
we have the results of this lemma.

Lemma 12. *For ,
*

*Proof. *From Lemma 7 we have that
It follows from Lebesgue theorem that
Finally, implies that
Combing (49) and (50), we complete the proof of this lemma.

Lemma 13. * has continuous derivatives up to second order on as follows:
**
where .*

*Proof. *Equation (51) can be obtained by
and Lemma 7, immediately. From (24) we have that
and so (52) holds.

Lemma 14. *There exist and such that
*

*Proof. *From (41) and , we have that
And since , let satisfy
Set
From , we have that and
On the other hand, from (10), (38), and Lemma 11, we have that
for , .

This means that
for , . It follows from Lemma 13 and (58) that
Now, from (59)–(62) we have (55), where

Lemma 15. *If , then for . If , then there exists , such that for and for .*

*Proof. *It follows from Lemma 14 that if
and then
By (40), (42), and (51) we can obtain that
With (10) and (41), (66) implies that
If , then from Lemma 12 and (64)–(67) we have the results of this lemma, immediately. If , then by Lemmas 12 and 14 we have that for near , and so for near . Thus, it follows from (64)–(67) that for .

*Proof of Theorem 5. *From Lemmas 6, 8, 9, and 15, we can obtain the results of Theorem 5.

#### References

- A. Ambrosetti, H. Brezis, and G. Cerami, “Combined effects of concave and convex nonlinearities in some elliptic problems,”
*Journal of Functional Analysis*, vol. 122, no. 2, pp. 519–543, 1994. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - P. Korman, Y. Li, and T. Ouyang, “Exact multiplicity results for boundary value problems with nonlinearities generalising cubic,”
*Proceedings of the Royal Society of Edinburgh A*, vol. 126, no. 3, pp. 599–616, 1996. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - P. Korman and T. Ouyang, “Exact multiplicity results for two classes of boundary value problems,”
*Differential and Integral Equations*, vol. 6, no. 6, pp. 1507–1517, 1993. View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - P. Korman and T. Ouyang, “Multiplicity results for two classes of boundary-value problems,”
*SIAM Journal on Mathematical Analysis*, vol. 26, no. 1, pp. 180–189, 1995. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - T. Laetsch, “The number of solutions of a nonlinear two point boundary value problem,”
*Indiana University Mathematics Journal*, vol. 20, pp. 1–13, 1970. View at Publisher · View at Google Scholar · View at MathSciNet - J. Smoller and A. Wasserman, “Global bifurcation of steady-state solutions,”
*Journal of Differential Equations*, vol. 39, no. 2, pp. 269–290, 1981. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - S.-H. Wang and D.-M. Long, “An exact multiplicity theorem involving concave-convex nonlinearities and its application to stationary solutions of a singular diffusion problem,”
*Nonlinear Analysis. Theory, Methods & Applications A*, vol. 44, pp. 469–486, 2001. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - L. Q. Zhang, “Uniqueness of positive solutions of $\mathrm{\Delta}u+u+{u}^{p}=0$ in a ball,”
*Communications in Partial Differential Equations*, vol. 17, no. 7-8, pp. 1141–1164, 1992. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - Z. Liu, “Exact number of solutions of a class of two-point boundary value problems involving concave and convex nonlinearities,”
*Nonlinear Analysis. Theory, Methods & Applications A*, vol. 46, pp. 181–197, 2001. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - Z. Liu and X. Zhang, “A class of two-point boundary value problems,”
*Journal of Mathematical Analysis and Applications*, vol. 254, no. 2, pp. 599–617, 2001. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet - J. Cheng, “Exact number of positive solutions for a class of semipositone problems,”
*Journal of Mathematical Analysis and Applications*, vol. 280, no. 2, pp. 197–208, 2003. View at Publisher · View at Google Scholar · View at Zentralblatt MATH · View at MathSciNet