Đáp án:
\(\dfrac{{133}}{8}\)
Giải thích các bước giải:
\(\begin{array}{l}
C = {x^2} - 10xy + 25{y^2} + 4{x^2} - 12xy + 9{y^2} - {x^3} + 3{x^2}y - 3x{y^2} + {y^3} - 8{x^3} + 12{x^2}y - 18x{y^2} - 12{x^2}y + 18x{y^2} - 27{y^3}\\
= - 9{x^3} - 26{y^3} + 5{x^2} - 22xy + 34{y^2} + 3{x^2}y - 3x{y^2}\\
Thay:x = \dfrac{1}{2};y = - \dfrac{1}{2}\\
\to C = - 9.{\left( {\dfrac{1}{2}} \right)^3} - 26{\left( { - \dfrac{1}{2}} \right)^3} + 5.{\left( {\dfrac{1}{2}} \right)^2} - 22.\dfrac{1}{2}.\left( { - \dfrac{1}{2}} \right) + 34.{\left( { - \dfrac{1}{2}} \right)^2} + 3.{\left( {\dfrac{1}{2}} \right)^2}.\left( { - \dfrac{1}{2}} \right) - 3.\left( {\dfrac{1}{2}} \right).{\left( { - \dfrac{1}{2}} \right)^2}\\
= \dfrac{{133}}{8}
\end{array}\)
