Expand the following:

$(-x+2 y-3 z)^{2}$

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

$x^{3}+27$

Classify the following as linear, quadratic or cubic polynomial

$4 y+11$

If $x^{2}-8 x-20=(x+a)(x+b),$ then $a b=\ldots \ldots \ldots$

Which of the following expressions are polynomials in one variable and which are not $?$ State reason for your answer. If the given expression is a polynomial, state whether it is a polynomial in one variable or not

$5 x^{2}-7 x+3 \sqrt{x}$