试明：若级数[tex=4.429x2.714]ySadpvq7BrEZCGdcnD6+aYYKMve96JE4sd3o4QbcQhyFEB8wySY9WvLLExFxYbd4[/tex]及[tex=4.0x2.714]ySadpvq7BrEZCGdcnD6+aZmrAzqw84m41cRzSztSWcBTzzE1dPl749vdarS2YDQV[/tex]皆收敛且[tex=11.071x1.286]KEk9vvqmh+CBNh5nnxa46HqdwXfcZ7FgwC5TRAiXnHCxUdO0AP0u57VybKAorlBU12GvShicsM4yb7ZMMzYXHg==[/tex]，则级数[tex=4.0x2.714]ySadpvq7BrEZCGdcnD6+aeoIzvM7G7HHNcjbk992lZRvUS0Xh/lotVqiUMKn/3kW[/tex]也收敛，若级数 [tex=1.571x1.357]hjG9g3d/QK7lH8zZx+2L/Q==[/tex]与[tex=1.5x1.357]QON3ZX8tDpa8hcC8KI55XA==[/tex]皆发散，问级数[tex=1.5x1.357]jW5HUp91iXA6ZnNyC/+CoQ==[/tex]的收敛性若何？提示：(1)先证级数[tex=5.5x2.714]ySadpvq7BrEZCGdcnD6+aRrMeIUlIOH1QB+K47pqlk3PJyHm4zPMgvDT8ndQ74qKuwSRORSNDNzjOlQ26lPWRw==[/tex]收敛。(2)可能收敛，也可能发散。例如[tex=11.643x2.357]ozp+yD1eymb4/EK2UAZZC9r19Jhg5MU9Rjw7GnxmzJSPaUrcZlSER0YjHa9TokIA11573J3i6NzMPGTxnbTueQ==[/tex][tex=5.643x1.357]NGWbQ9xjBbPjETUZQumFRw/fmak//iRLrHzvWXLffDA=[/tex]。