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已知函数f(X)=1/x-1/2,则f(1/11)×f(2/11)×f(3/11)……f(21/11)=

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已知函数f(X)=1/x-1/2,则f(1/11)×f(2/11)×f(3/11)……f(21/11)=
已知函数f(X)=1/x-1/2,则f(1/11)×f(2/11)×f(3/11)……f(21/11)=
f(1/11)×f(2/11)×f(3/11)……f(21/11)
=(11-1/2)* (11/2-1/2)* (11/3-1/2)* (11/4-1/2)*……* (11/21-1/2)*
=[(22-1)/(2*1)]*[(22-2)/(2*2)]* [(22-3)/(2*3)]*[(22-4)/(2*4)]*……*[(22-21)/(2*21)]
=[21/(2*1)]*[20/(2*2)]* [19/(2*3)]*[18/(2*4)]*……*[1/(2*21)]
=[21*20*19*18*……*1] / [(2*1)*(2*2)*(2*3)*(2*4)*……*(2*21)]
=21!/(2^21*21!)
=1/2^21