a) B = 3x³ - 2y³ - 6x²y²
B = 3x³ - ( 2y³ + 6x²y²) = 3x³ - 2y²( y + 3x²)
x =$\frac{2}{3}$ , $\frac{1}{2}$ ta có:
B = 3 . ($\frac{2}{3}$ )³ - 2 . ( $\frac{1}{2}$ )² . ( $\frac{1}{2}$ + 3. $\frac{4}{9}$ = $\frac{55}{36}$
b) C = 2x + xy² - x²y - y
C = ( 2x + xy²) - ( x²y - y)
C = x ( 2+ y²) - y ( x² + 1)
x = $\frac{-1}{2}$, y = $\frac{-1}{3}$ ta có:
C = ( $\frac{-1}{2}$ [ 2 + ($\frac{-1}{3}$ )²] - ( $\frac{-1}{3}$ ) [ ($\frac{-1}{2}$ )²+ 1]
C = ( $\frac{-19}{18}$ ) - ($\frac{-5}{12}$)
C = $\frac{-23}{36}$
# Bạn tham khảo ạ.
Chúc bạn học tốt.
