2 câu trả lời
`A=1+2+4+8+16+...+8192`
`⇒A=1+2+2^2+2^3+2^4+...+2^13`
`⇒2A=2+2^2+2^3+2^4+2^5+...+2^14`
`⇒2A-A=(2+2^2+2^3+2^4+2^5+...+2^14)-(1+2+2^2+2^3+2^4+...+2^13)`
`⇒A=2^14-1`
`A=1+2+4+8+16+...+8192`
`⇒A=1+2+2^2+2^3+2^4+...+2^13`
`⇒2A=2+2^2+2^3+2^4+2^5+...+2^14`
`⇒2A-A=(2+2^2+2^3+2^4+2^5+...+2^14)-(1+2+2^2+2^3+2^4+...+2^13)`
`⇒A=2^14-1`