Question

为什么导数公式是(ln x)'=1/x ,实际运用时是(ln x)'=1/x*x'

Answer 1

(ln x)'=(1/x)*x'

= 1/x ( x' =1 )

let z = 2x^2+3x+1

dz/dx = 4x+3

y=ln(2x^2+3x+1)

dy/dx = (dy/dz ) .dz/dx

= [1/(2x^2+3x+1)] (4x+3)