Evaluate

$(555)^{2}$

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

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

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

Evaluate the following products without multiplying directly

$78 \times 84$

Classify the following as linear, quadratic or cubic polynomial

$5-3 t$