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

$5-7 x-3 x^{2}$

Which of the following expressions is a polynomial, state the reason ? If an expression is polynomial, state whether it is a polynomial in one variable or not

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

From the following polynomials find out which of them has $(x-1)$ as a factor

$2 x^{3}+5 x^{2}-x-6$

Expand

$(2 x-y-5)^{2}$

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

$x^{2}+x+1$