Factorise the expression: $a{m}^2+b{m}^2+b{n}^2+a{n}^2$

Write the factorised form of $\left(lm+l\right)+m+1$

The factorised form of $5y^2-20y-8z+2yz$ is $\left(y-k\right)\left(5y+2z\right)$. Then find the value of $k$.

Write the factorised form of $10ab+4a+5b+2$

Write the factorised form of $6xy-4y+6-9x$

The factorised form of $a^4-b^4$ is $\left(a-b\right)\left(k\right)\left(a^2+b^2\right)$. Find the value of $k$.

The factorised form of $p^4-81$ is $\left(p-3\right)\left(k\right)\left(p^2+9\right)$. Find the value of $k$.

If $x^4-{\left(y+z\right)}^4$ can be factorised as $\left(x+y+z\right)\left(x-y-z\right)\left(x^2+{\left(y+z\right)}^m\right)$, then what is the value of $m$?