# A FUNCTIONAL EQUATION RELATED TO QUADRATIC FORMS WITHOUT THE CROSS PRODUCT TERMS

• Accepted : 2008.04.10
• Published : 2008.06.25

#### Abstract

In this paper, we obtain the general solution and the stability of the 2-dimensional vector variable quadratic functional equation f( x + y, z - w) + f(x - y, z + w) = 2f(x, z ) + 2f(y, ${\omega}$). The quadratic form f( x, y) = $ax^2$ + $by^2$ without cross product terms is a solution of the above functional equation.

#### References

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#### Cited by

1. A Fixed Point Approach to the Stability of a Functional Equation vol.50, pp.4, 2010, https://doi.org/10.5666/KMJ.2010.50.4.557