Factorize the following expressions:

$\Delta 4 x^{2}-y^{4}$

$\triangleright 8 x^{2}-24 x y+18 y^{2}$

$\Delta(x-y)(3 x+1)-2\left(x^{2}-y^{2}\right)-(y-x)^{2}$
$$
\begin{aligned}
& \triangleright 4 x^{2}-y^{4}=(2 x)^{2}-\left(y^{2}\right)^{2}=\left(2 x+y^{2}\right)\left(2 x-y^{2}\right) \\
& \triangleright 8 x^{2}-24 x y+18 y^{2}=2\left((2 x)^{2}-2(2 x)(3 y)+(3 y)^{2}\right)=2(2 x-3 y)^{2} \\
& \triangleright(x-y)(3 x+1)-2\left(x^{2}-y^{2}\right)-(y-x)^{2}=(x-y)(3 x+1-2(x+y)-(x-y))=(x-y)(1-y)
\end{aligned}
$$