What is the number of functions whose range is {2,5,10}, where the corresponding relation is y = x ^ 2 + 1 A.1 B.8 C.27 D.39 This is the joint examination of ten schools in Ningbo, Zhejiang Province in 2009

27
Because there are three methods of function value 2 corresponding to independent variable, which are 1; - 1; 1, - 1
There are three ways for function value 5 to correspond to independent variable, which are 2; - 2; 2, - 2
There are three methods for function value 10 corresponding to independent variable, which are 3; - 3; 3, - 3
So the number of functions is 3 times 3 times 3 = 27

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