1.
a) A = 2x².$\frac{1}{2}$ . y³ - 1$\frac{1}{4}$. y. .$\frac{4}{5}$.x².y²
= x² . y³ - $\frac{5}{4}$.$\frac{4}{5}$ . x² . y³
= x² . y³ - x² . y³
=0
b) B = $\frac{1}{2}$ a³. b² + ($\frac{4}{3}$. ab²). ($\frac{-1}{2}$.a²)
= $\frac{1}{2}$ a³. b² + $\frac{4}{3}$. $\frac{-1}{2}$. a³.b²
= $\frac{1}{2}$ a³. b² + $\frac{-2}{3}$. a³.b²
= a³. b². ($\frac{1}{2}$+ $\frac{-2}{3}$)
= a³. b² . $\frac{-1}{6}$
2.
Nhóm 1: 5x²y; $\frac{1}{3}$x²y
Nhóm 2: -3xy²; $\frac{1}{5}$xy²
Nhóm 3: -3a²b; -2a²b
3.P= $\frac{3}{2}$. mn² -$\frac{5}{8}$.mn² + $\frac{1}{8}$.mn² - $\frac{3}{16}$.mn²
= { $\frac{3}{2}$ - $\frac{5}{8}$+ $\frac{1}{8}$- $\frac{3}{16}$} .mn²
= $\frac{13}{16}$.mn²
Thay m=2;n=-1 ta có:
P= $\frac{13}{16}$.2.1= $\frac{13}{8}$
