CHÚC BẠN HỌC TỐT !!
1)
a) $(5x+3y)^2 = (5x)^2 + 2.5x.3y + (3y)^2 = 25x^2 + 30xy + 9y^2$
b) $ (-3x+2)^2 = (-3x)^2 + 2.(-3x).2 + 2^2 = 9x^2 - 12x + 4$
c) $ (\dfrac{2}{3x}+ \dfrac{1}{3z})^2 = \dfrac{4}{9x^2} + \dfrac{4}{9zx} + \dfrac{1}{9z^2}$
d) $(0,01 +xy)^3 = (0,01)^3 + 3.(0,01)^2.xy+3.0,01.(xy)^2 +(xy)^3$
$= \dfrac{1}{1000000} + \dfrac{3xy}{10000} + 0,03.x^2y^2 +x^3y^3 $
2)
a) $x^2-81 = x^2 -9^2 = (x-9).(x+9)$
b) $27x^3+a^3b^3 = (3x)^3 + (ab)^3 = (3x+ab)(9x^2-3xab+a^2b^2)$