( x² + $\frac{2}{5}$y ) ( x² - $\frac{2}{5}$y )
= ( x² )²- ($\frac{2}{5}$ y)²
= $x^{4}$ - $\frac{4}{25}$$y^{2}$
($\sqrt[]{2x}$ - 2y )$^{2}$
= ( ($\sqrt[]{2x}$ )² - 2 . $\sqrt[]{2x}$ . 2y + ( 2y )²
= 2x - 4y($\sqrt[]{2x}$ + 4y²
($\sqrt[]{2x}$ + $\sqrt[]{8y}$ )$^{2}$
= ($\sqrt[]{2x}$ )² + 2 . $\sqrt[]{2x}$ . $\sqrt[]{8y}$ + ( $\sqrt[]{8y}$ )²
= 2x + 8$\sqrt[]{xy}$ + 8y
( $\frac{x}{2}$ + 2$y^{2}$ ) ( $\frac{x}{2}$ - 2$y^{2}$)
= ($\frac{x}{2}$ ) $^{2}$ - (2y$^{2}$ )$^{2}$
= $\frac{x^{2}}{4}$ - 4y$^{4}$
( x + $\frac{1}{6}$y + 3 )²
= x² + ($\frac{1}{6}$y)² +3² + 2 . x . $\frac{1}{6}$y + 2 . $\frac{1}{6}$y . 3 + 2 . x . 3
= x² +$\frac{1}{36}$ y$^{2}$ + 9 + $\frac{1}{3}$xy + y + 6x
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