在高等数学中，若函数f(x)在区间[a,b]上连续，且f(a)与f(b)异号，则根据零点定理，在区间(a,b)内至少存在一点ξ，使得f(ξ)_。
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Correct answer
C. 等于零
Principle or equation
零点定理：若函数在闭区间上连续，且端点函数值异号，则至少存在一点使函数值为零。
Why this answer is correct
零点定理保证存在ξ∈(a,b)使得f(ξ)=0。
Example
f(x)=x-1在[0,2]上连续，f(0)=-1，f(2)=1，异号，所以存在ξ=1使f(ξ)=0。
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