Factorise the following expression:  $7a^2+14a$

The factorised form of the expression $-16z+20z^3$ is $k\left(4-5z^2\right)$.What is the value of $k$?

Write the factorised form of the following expression:

$20l^{2}m+30alm$

Write the factorised form of the following expression.

$5x^{2}y-15x{y}^2$

Factorise the following expression: $10a^2-15b^2+20c^2$ 

Write the factorised form of the following expression.

$-4a^2+4ab-4ca$

Write the factorised form of the following expression.

$x^{2}yz+x{y}^{2}z+xy{z}^2$

Write the factorised form of the following.

$a{x}^{2}y+bx{y}^2+cxyz$