a, 10x ( x - y) -8y (y -x)
= 10x(x - y) + 8y(x - y)
= (x - y)(10x + 8y)
= 2(x - y)(x + y)
b, 2x (x + 3) + 2 (x + 3)
= (x + 3)(2x + 2)
= 2(x + 1)(x + 3)
c, 4x ( x - 2y) + 8y (2y - x)
= 4x(x - 2y) - 8y(x - 2y)
= (x - 2y)(4x - 8y)
= 4(x - 2y)(x - 2y)
= 4(x - 2y)²
d, ( x + y)³ - x ³ - y ³
= (x + y)³ - (x³ + y³)
= (x + y)³ - (x + y)(x² - xy + y²)
= (x + y)[(x + y)² - (x² - xy + y²)]
= (x + y)(x² + 2xy + y² - x² + xy - y²
= 3xy(x + y)
e, y ² ( x ² + y) - zx ² - zy
y²(x² + y) - z(x² + y)
= (x² + y)(y² - z)
f, 1/2x ( x ² - 4) + 4 ( x + 2)
= $\frac{1}{2}$x(x - 2)(x + 2) + 4(x + 2)
= (x + 2)[ $\frac{1}{2}$x(x - 2) + 4]
= (x + 2)( $\frac{1}{2}$x² - 1 + 4)
= (x + 2)( $\frac{1}{2}$x² - 3)
g, 4x ³y - 9xy
= xy(4x² - 9)
= xy[(2x)² - 3²]
= xy(2x - 3)(2x + 3)