`\color{#FF6F6F}{⋆} \color{#FFF0F0}{p} \color{#FFE0E0}{h} \color{#FFD0D0}{ư} \color{#FFBABA}{ơ} \color{#FFA3A3}{n} \color{#FF8A8A}{g} \color{#FF6F6F}{l} \color{#FF5252}{i} \color{#FF3333}{n} \color{#FF1414}{h}`Đáp án `+` Giải thích các bước giải:

a)

$x^2 + 4x + 4$

$= x^2 + 2 \cdot x \cdot 2 + 2^2$

$= (x + 2)^2$

b)

$x^2 - 6x + 9$

$= x^2 - 2 \cdot x \cdot 3 + 3^2$

$= (x - 3)^2$

c)

$4x^2 + 12x + 9$

$= (2x)^2 + 2 \cdot 2x \cdot 3 + 3^2$

$= (2x + 3)^2$

d)

$9x^2 - 24xy + 16y^2$

$= (3x)^2 - 2 \cdot 3x \cdot 4y + (4y)^2$

$= (3x - 4y)^2$