求不了,只能求S=1×1!+2×2!+3×3!+……+n×n!=(2-1)x1!+2x2!+3x3!+4x4!+.+nxn!=2!-1+2x2!+3x3!+4x4!+.+nxn!=(1+2)x2!-1+3x3!+4x4!+.+nxn!=3!-1+3x3!+4x4!+.+nxn!=(1+3)x3!-1+4x4!+.+nxn!=4!-1+5x5!+.+nxn!.=(n+1)!-...