( x - 1/3)^4

Lời giải:

\({\left( {x - \frac{1}{3}} \right)^4}\)\( = {\left[ {x + \left( { - \frac{1}{3}} \right)} \right]^4}\)

\( = {x^4} + 4.{x^3}.\left( { - \frac{1}{3}} \right) + 6.{x^2}.{\left( { - \frac{1}{3}} \right)^2} + 4.x.{\left( { - \frac{1}{3}} \right)^3} + {\left( { - \frac{1}{3}} \right)^4}\)

\( = {x^4} - \frac{4}{3}{x^3} + \frac{2}{3}{x^2} - \frac{4}{{27}}x + \frac{1}{{81}}\).