(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15=?

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(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15=?
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(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15=?
(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15=?

(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15=?
(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15
(1-1/2)(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)/(1-1/2)
=(1-1/2^16)/(1/2)=2(1-1/2^16)=2-1/2^15
(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15
=2-1/2^15+1/2^15
=2

平方差公式的运用

在式子前面乘以(1-1/2)利用平方差公式可求得答案

原式=(1-1/2)(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)/(1-1/2)
=(1-1/2^16)/(1/2)=2(1-1/2^16)

=2-1/2^15(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15

=2-1/2^15+1/2^15

=2