Đáp án:
Giải thích các bước giải:
9.$\left (x^2+\frac{2}{5}y \right )\left (x^2-\frac{2}{5}y \right )$
$=(x^2)^2-\left (\frac{2y}{5} \right )^2$
$=x^4-\frac{4y^2}{25}$
10.$\left (\frac{x}{2}-y \right )\left (\frac{x}{2}+y \right )$
$=\left (\frac{x}{2} \right )^2 - y^2$
$=\left (\frac{x^2}{4} \right ) - y^2$
$15. \left (x+\frac{1}{6}y+3 \right )^2$
$=\left [(x+\frac{1}{6}y)+3 \right ]^2$
$=\left (x+\frac{1}{6}y \right )^2 +6\left (x+\frac{1}{6}y \right ) + 9$
$=x^2+ \frac{1}{3}xy + \frac{1}{36} + 6x+y+9$
$17.\left (\frac{x}{2}+2y^2 \right )\left (\frac{x}{2}-2y^2 \right )$
$=\left (\frac{x}{2} \right )^2 - (2y^2)^2$
$=\frac{x^2}{4} - 4y^4$
Chúc bạn học tốt.
