Affiliation:
1. Department of Mathematics , Faculty of Sciences and Techniques , S. M. Ben Abdellah University , B.P. 2202 , Fez , Morocco
Abstract
Abstract
Let 𝑆 be a commutative semigroup, 𝐾 a quadratically closed commutative field of characteristic different from 2, 𝐺 a 2-cancellative abelian group and 𝐻 an abelian group uniquely divisible by 2.
The goal of this paper is to find the general non-zero solution
f
:
S
2
→
K
f\colon S^{2}\to K
of the d’Alembert type equation
f
(
x
+
y
,
z
+
w
)
+
f
(
x
+
σ
(
y
)
,
z
+
τ
(
w
)
)
=
2
f
(
x
,
z
)
f
(
y
,
w
)
,
x
,
y
,
z
,
w
∈
S
,
f(x+y,z+w)+f(x+\sigma(y),z+\tau(w))=2f(x,z)f(y,w),\quad x,y,z,w\in S,
the general non-zero solution
f
:
S
2
→
G
f\colon S^{2}\to G
of the Jensen type equation
f
(
x
+
y
,
z
+
w
)
+
f
(
x
+
σ
(
y
)
,
z
+
τ
(
w
)
)
=
2
f
(
x
,
z
)
,
x
,
y
,
z
,
w
∈
S
,
f(x+y,z+w)+f(x+\sigma(y),z+\tau(w))=2f(x,z),\quad x,y,z,w\in S,
the general non-zero solution
f
:
S
2
→
H
f\colon S^{2}\to H
of the quadratic type equation
f
(
x
+
y
,
z
+
w
)
+
f
(
x
+
σ
(
y
)
,
z
+
τ
(
w
)
)
=
2
f
(
x
,
z
)
+
2
f
(
y
,
w
)
,
x
,
y
,
z
,
w
∈
S
,
f(x+y,z+w)+f(x+\sigma(y),z+\tau(w))=2f(x,z)+2f(y,w),\quad x,y,z,w\in S,
where
σ
,
τ
:
S
→
S
\sigma,\tau\colon S\to S
are two involutions.
Subject
Applied Mathematics,Numerical Analysis,Analysis