Ax2=1x2/1x2x3+1x2/2x3x4+...+1x2/48x49x50
Ax2=1/1x2-1/2x3+1/2x3-1/3x4+...+1/48x49-1/49x50
Ax2=1/1x2-1/49x50
Ax2=1/2-1/2450
Ax2=1225/2450-1/2450
Ax2=1224/2450
A=1224/2450:2
A=1224/2450X1/2
A=1224/4900
A=306/1225
Còn câu trả lời nào khác ko zậy !?!
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