$4x^{2} - 20x + 25 = (\ldots \ldots \ldots)^{2}$

Factorise the following:
$9 x^{2}+4 y^{2}+16 z^{2}+12 x y-16 y z-24 x z$

Without actual division,prove that $2x^4 - 5x^3 + 2x^2 - x + 2$ is divisible by $x^2 - 3x + 2$.

Expand $(x+5y)(x-5y)$.

State whether the following statement is True or False. Justify your answer.
Every polynomial is a binomial.

Which of the following expressions are polynomials in one variable and which are not? State the reason for your answer. If the given expression is a polynomial,state whether it is a polynomial in one variable or not.
$x^{2} + x - 3 + \frac{4}{x}$