=x(x^2-3x+6)

=x^3-3x^2+6x

∴y′=3x^2-6x+6

2. Solution: ∵ According to the derivative rule of composite function, there are

g′(x)=[f(x)/x]′

=[xf′(x)-f(x)]/(x^2)

∴g′(5)=[5*f′(5)-f(5)]/(5^2)

=(5*3-4)/25

= 1 1/25

The key to mathematics is to practice more. Practice makes perfect. I hope I can help you ~