Question

曲线y=xⁿ在x=2处的导数为12,则n等于(    )

A.1                 B.2                 C.3                  D.4

Answer 1

答案：C  ∵f′(x)=nx^n-1,∴f′(2)=n·2^n-1.令n·2^n-1=12,验证得n=3.