Đáp án:
Giải thích các bước giải:
$a) (x+2y)^2$
$= x^2 + 2.x.2y + (2y)^2$
$= x^2+4xy+4y^2$
$b) (x-2).(x^2+2x+4)$
$= (x-2)(x^2+2x+2^2)$
$=x^3-2^3$
$=x^3-8$
$c) (x+\dfrac{1}{3})^3$
$= x^3+3.x^2.\dfrac{1}{3} + 3.x.(\dfrac{1}{3})^2+(\dfrac{1}{3})^3$
$= x^3+x^2+3x.\dfrac{1}{9}+\dfrac{1}{27}$
$=x^3+x^2+\dfrac{1}{3}x+\dfrac{1}{27}$
$d) (\dfrac{x}{2} - y )(\dfrac{x}{2}+y)$
$= (\dfrac{x}{2})^2 - y^2$
$=\dfrac{x^2}{4}-y^2$