When completing the square is carried out on the quadratic [tex]x^2+11x[/tex] we get
[tex]x^2+11x+\dfrac{121}{4}[/tex]
when expressed as a binomial squared, we get
[tex]\left(x+\dfrac{11}{2}\right)^2[/tex]
To complete the square, we need to add a term to the expression
[tex]x^2+11x[/tex]
that would make it a perfect square. Generally, given the quadratic expression
[tex]x^2+bx[/tex]
to make it a perfect square, we have to add half the square of the coefficient of [tex]x[/tex]. That is, add [tex]\left(\frac{b}{2}\right)^2[/tex], or [tex]\frac{b^2}{4}[/tex] to the quadratic expression to get
[tex]x^2+bx+\dfrac{b^2}{4}[/tex]
which, when factored into a binomial squared becomes
[tex]\left(x+\dfrac{b}{2}\right)^2[/tex]
In our case, the quadratic [tex]x^2+11x[/tex] will become
[tex]x^2+11x+\dfrac{121}{4}[/tex]
and when expressed as a binomial squared, we get
[tex]\left(x+\dfrac{11}{2}\right)^2[/tex]
Learn more about completing the square here https://brainly.com/question/2055939