Đặt \(A=2+2^2+2^3+...+2^{15}\)
\(\Rightarrow2A=2^2+2^3+2^4...+2^{15}+2^{16}\)
\(\Rightarrow2A-A=\left(2^2+2^3+2^4+...+2^{16}\right)-\left(2+2^2+2^3+...+2^{15}\right)\)
\(\Rightarrow2A-A=A=2^{16}-2\)
Vậy \(2+2^2+2^3+...+2^{15}=2^{16}-2\)
2+22 +23+24+......+215
Gọi tên biểu thức trên là A
A=2+22 +23+24+......+215
2.A=2.(2+22 +23+24+......+215)
2.A=22 +23+24+......+215+216
2.A-A=(22 +23+24+......+215+216)-(2+22 +23+24+......+215)
A=22 +23+24+......+215+216-2-22-23-24+......-215
A=216-2
A=65534
Bài giải
Đặt \(A=2+2^2+2^3+...+2^{15}\)
\(2A=2^2+2^3+2^4+...+2^{16}\)
\(2A-A=2^{16}-2\)
\(A=2^{16}-2\)