Classify the following polynomials as polynomials in one variable, two variables etc.

$x y+y z+z x$

Expand

$\left(x-\frac{1}{2}\right)^{2}$

Using suitable identity, evaluate the following:

$101 \times 102$

Multiply $x^{2}+4 y^{2}+z^{2}+2 x y+x z-2 y z$ by $(-z+x-2 y)$

Write the coefficients of $x^{2}$ in each of the following polynomials

$4+7 x+3 x^{2}$

Write the following cubes in expanded form

$(7 x-4 y)^{3}$