Đáp án:
Giải thích các bước giải:
đặt `A=1xx3xx5+3xx5xx7+5xx7xx9+....+95xx97xx99`
`->8A=1xx3xx5xx8+3xx5xx7xx8+5xx7xx9xx8+....+95xx97xx99xx8`
`->8A=1xx3xx5xx(7+1)+3xx5xx7xx(9-1)+5xx7xx9xx(11-3)+....+95xx97xx99xx(101-93)`
`->8A=1xx3xx5xx7+1xx3xx5+3xx5xx7xx9-1xx3xx5xx7+5xx7xx9xx11-3xx5xx7xx9+.....+95xx97xx99xx101-93xx95xx97xx99`
`->8A=95xx97xx99xx101+15`
`->A=(95xx91xx99xx101+15)/8`
$@Kate2007$
#anh em siêu nhân