Find the zero of the following polynomial.

$p\left(t\right)=at, a\ne 0, a$ is a real constant number.

Find the zero of the following polynomial.

$p\left(r\right)=cr+d, c\ne 0, c, d$ are real constant numbers.

Find the zero of the following polynomial.

$p\left(u\right)=3u-6$

Find the zero of the following polynomial.

$r\left(s\right)=2s+3$

If zero of the polynomial $p\left(x\right)=\sqrt{5}-x$ is $\sqrt{k}$, then find the value of $k.$

Find the zero of the following polynomial.

$q\left(t\right)=\frac{1}{2}t-\frac{2}{3}$

Find the sum and difference of the following polynomials and give the degree of the resultant.

$p\left(y\right)=y^2+5y, q\left(y\right)=3y-5$

Find the sum and difference of the following polynomials and give the degree of the resultant.

$p\left(r\right)=5r^2-9, s\left(r\right)=9r^2-4$

Find the sum and difference of the following polynomials and give the degree of the resultant.

$p\left(y\right)=15y^4-5y^2+27, s\left(y\right)=15y^4-9$