Se considera f:R-R,f(x)=(x-1)(x-2)(x-3)+2.
Calculati f'(3).


Răspuns :

După eliminarea parantezelor și reducerea termenilor asemenea,

se obține:

[tex] \it f(x) = x^3-6x^2+11x-4
\\ \\
f'(x) = 3x^2-12x+11
\\ \\\
f'(3) = 3\cdot3^2-12\cdot3+11=27-36+11=38-36=2 [/tex]



[tex] f(x)=(x-1)(x-2)(x-3)+2\\
(x-1)(x-2)(x-3)+2=(x^{2}-2x-x+2)(x-3)+2=(x^{2}-3x+2)(x-3)+2=\\
=x^{3}-3x^{2} -3x^{2}+9x+2x-6+2=x^{3} -6x^{2} +11x-4\\
f(x)=x^{3} -6x^{2} +11x-4\\
f^{'}(x)=(x^{3} -6x^{2} +11x-4)^{'}=(x^{3})^{'}-(6x^{2})^{'}+(11x)^{'}-4^{'}=3x^{2} -12x+11-0=3x^{2} -12x+11\\
f^{'}(x)=3x^{2} -12x+11\\ f^{'}(3)=3*3^{2}-12*3+11=27-36+11=2 [/tex]