a, ($\frac{x}{2}$-y)($\frac{x}{2}$+y)= ($\frac{x}{y}$)$^{2}$-$y^{2}$
b, $x^{2}$+2x+1=$(x+1)^{2}$
c, 1-4x+$4x^{2}$=$(1-2x)^{2}$
d, $9x^{4}$+$16y^{6}$-$24x^{2}$ $y^{3}$=($3x^{2}$ - $4y^{3}$)
e, (x-2)($x^{2}$+2x+4)=$x^{3}$+$2^{3}$
f, (5x-y)($25x^{2}$+5xy+$y^{2}$)
g, $8x^{3}$+$12x^{2}$+6x+1=$(2x+1)^{3}$
h, 1-9x+$27x^{2}$-$27x^{3}$=$(1-3x)^{3}$
cho mik xin ctlhn nha