Question

若曲線y=x⁴的一條切線l的斜率是4，則切線l的方程為

A.4x-y-3=0                                       B.x+4y-5=0

C.4x-y+3=0                                       D.x+4y+3=0

Answer 1

A

解析:∵y′=(x⁴)′=4x³,且l的斜率是4,∴4x³=4.∴x=1.

y=1⁴=1,∴切點為(1,1).

則l的方程為4(x-1)=y-1,即4x-y-3=0.

選A.