Factorise

$4 x^{2}+9 y^{2}+49 z^{2}-12 x y+42 y z-28 z x$

If $49 x^{2}-b=\left(7 x+\frac{1}{2}\right)\left(7 x-\frac{1}{2}\right),$ then the value of $b$ is

Classify the following as a constant, linear,quadratic and cubic polynomials:

$t^{2}$

Classify the following as a constant, linear quadratic and cubic polynomials:

$2-x^{2}+x^{3}$

Factorise the following:

$16 x^{2}+4 y^{2}+9 z^{2}-16 x y-12 y z+24 x z$