Evaluate the following product without multiplying directly:
$78 \times 84$

If $(5x - 3)^2 = 25x^2 + kx + 9$,then find $k$.

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

Expand the following:
$(-x+2y-3z)^{2}$

State whether the following statement is true or false:
The degree of the polynomial $5x^{2} - 7x + 2$ is $5$.

If $p(x) = x^{2} - 2\sqrt{2}x + 1$,then $p(2\sqrt{2})$ is equal to