To find the square of the algebraic expression given below. Using ${\left(a-b\right)}^2=a^2-2ab+b^2$, what has to be substituted for a and b and hence find the square.

$999$

To find the square of the algebraic expression given below. Using ${\left(a-b\right)}^2=a^2-2ab+b^2$, what has to be substituted for a and b and hence find the square.

$p+q-r-s$

Which one of the following will be equal to the product of $\left(\mathrm{a}+\mathrm{b}\right)\times \left(\mathrm{a}+\mathrm{b}\right) ?$

Let's find, which of the following will be the value for $k$ satisfying the identity ${\left(x+7\right)}^2=x^2+14x+k$.

Which one of the following algebraic expression must be added to $a^2+b^2$, so that the sum is perfect square. Let's find.

If ${\left(a+b\right)}^2=a^2+6a+9$, let's find, which of the following is the positive value of $b$.

let's find, which one of the following numbers when added to $x^2+\frac{1}{4}x$ makes it a perfect square.

Let's find, for which value or values of $k$, will the expression $c^2+kc+\frac{1}{9}$ be a perfect square.

Let's find what must be subtracted from $9p^2+\frac{1}{9p^2}$ to make it a perfect square.