1.1! +2.2! + 3.3! +4.4! +5.5! +6.6!
1.1 +2.(1.2)+3.(1.2.3)+4.(1.2.3.4)+5.(1.2.3.4.5)+6.(1.2.3.4.5.6)
1.1+2.2+3.6+4.24+5.120+6.720
1+4+18+96+600+4320
5039
\(1\cdot1!+2\cdot2!+3\cdot3!+4\cdot4!+5\cdot5!+6\cdot6!\)
\(=1\cdot1+2\cdot\left(1\cdot2\right)+3\cdot\left(1\cdot2\cdot3\right)+4\cdot\left(1\cdot2\cdot3\cdot4\right)+5\cdot\left(1\cdot2\cdot3\cdot4\cdot5\right)+6\cdot\left(1\cdot2\cdot3\cdot4\cdot5\cdot6\right)\)
\(=1+4+18+96+600+4320\)
\(=5039\)
Bấm máy tính là nó ra liền, theo hợp tổ phím SHIFT