CHÚC BẠN HỌC TỐT!!!!!
`N=1+3^2+3^4+........+3^{1000}`
`6N=3^2+3^4+3^6+........+3^{1002}`
`6N-N=(3^2+3^4+3^6+........+3^{1002})-(1+3^2+3^4+........+3^{1000})`
`5N=3^{1002}-1`
`N=(3^{1002}-1)/5`
`A=1+3+3^2+3^3+.....+3^{1000}`
`3A=3+3^2+3^3+3^4+.....+3^{1001}`
`3A-A=(3+3^2+3^3+3^4+.....+3^{1001})-(1+3+3^2+3^3+.....+3^{1000})`
`2A=3^{1001}-1`
`A=(3^{1001}-1)/2`
CHÚC BẠN HỌC TỐT!!!!!