\(1.1!+2.2!+3.3!+4.4!+5.5!\)
= \(\left(2-1\right).1!+\left(3-1\right).2!+\left(4-1\right).3!+\left(5-1\right).4!+\left(6-1\right).5!\)
= \(2!-1!+3!-2!+4!-3!+5!-4!+6!-5!\)
= \(6!-1!\) = \(720-1=719\)
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