Câu hỏi của sweetdream

Question

tính A=4+2mũ2+2mũ3+2mũ4+................+2mũ20

minhduc · Accepted Answer

$A=4+2^2+2^3+..+2^{20}$$\Rightarrow2A=8+2^3+2^4+...+2^{21}$$\Rightarrow2A-A=\left(2^3+2^3+....+2^{21}\right)-\left(2+2+2^2+...+2^{20}\right)$$\Rightarrow A=\left(2^3+2^{21}\right)-\left(2+2+2^2\right)$$\Rightarrow A=2^{21}+8-8$$\Rightarrow A=2^{21}$Câu trả lời: $A=4+2^2+2^3+..+2^{20}$$\Rightarrow2A=8+2^3+2^4+...+2^{21}$$\Rightarrow2A-A=\left(2^3+2^3+....+2^{21}\right)-\left(2+2+2^2+...+2^{20}\right)$$\Rightarrow A=\left(2^3+2^{21}\right)-\left(2+2+2^2\right)$$\Rightarrow A=2^{21}+8-8$$\Rightarrow A=2^{21}$

chu thị quỳnh hoa · Answer

=2162688 nhaCâu trả lời: =2162688 nha

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