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integral equation

n. (context mathematics English) An equation involving a function f(x) and integrals of that function to be solved for f(x)

Wikipedia
Integral equation

In mathematics, an integral equation is an equation in which an unknown function appears under an integral sign.

There is a close connection between differential and integral equations, and some problems may be formulated either way. See, for example, Green's function, Fredholm theory, and Maxwell's equations.