Answer :
Given:
The expression is:
[tex]b^2+20b[/tex]
To find:
The a monomial so that the trinomial may be represented by a square of a binomial.
Solution:
If an expression is [tex]x^2+bx[/tex], then be need to add square of half of coefficient of x, i.e., [tex]\left(\dfrac{b}{2}\right)^2[/tex] in the given expression to make in perfect square.
We have,
[tex]b^2+20b[/tex]
Here, coefficient of b is 20,so wee need to add square of half of coefficient of b, i.e., [tex]\left(\dfrac{20}{2}\right)^2[/tex].
[tex]\left(\dfrac{20}{2}\right)^2=10^2[/tex]
[tex]\left(\dfrac{20}{2}\right)^2=100[/tex]
Therefore, we need to add 100 to make [tex]b^2+20b[/tex] a perfect square binomial.