Write the coefficient of $x^{2}$ in the following polynomial:
$5-7 x-3 x^{2}$

Factorise the expression: $x^{2} + \frac{y^{2}}{4} + \frac{z^{2}}{16} + xy + \frac{yz}{4} + \frac{zx}{2}$

Which of the following expressions is a polynomial? State the reason. If an expression is a polynomial,state whether it is a polynomial in one variable or not: $x^{2}+y^{2}+z^{2}+2xy+2yz+2zx$

Factorise:
$x^{2}+9x+18$

Evaluate the following product without multiplying directly: $76 \times 82$

Verify whether $3$ and $7$ are zeros of the polynomial $p(x) = x^{2} - 5x - 14$ or not.