$\left(3x-5y\right)^2-\left(3x+5y\right)^2$

$\frac23\left(6a-1{,}5b\right)^2$

$\left(0{,}5x-y\right)^2-\left(0{,}5x-y\right)\cdot\left(0{,}5x+y\right)$

$\left(\frac13x-2\right)^2+\frac13\cdot\left(x+2\right)^2$

$\left(2x-3\right)^2-2\cdot\left(x+3\right)^2-\frac12\cdot\left(6-2x\right)^2$

$\frac13\cdot\left(1{,}5a-b\right)^2-\frac34\cdot\left(\frac13b+a\right)^2$

$\left(a-0{,}4b\right)^2-2\cdot\left(0{,}3b-0{,}5a\right)^2+0{,}2\cdot\left(a+0{,}1b\right)^2$