(1+1/2)(1+1/2²)(1+1/2^4)(1+1/2^8)+1/2^ 1 5=2×(1-1/2)(1+1/2) (1+1/2²)(1+1/2^4)(1+1/2^8)+1/2^ 1 5=2×(1-1/2²)(1+1/2²)(1+1/2^4)(1+1/2^8)+1/2^ 1 5=2×(1-1/2^16)+1/2^15=2
