The number added to the polynomial is [tex]\frac{441}{4}[/tex]
Explanation:
The given polynomial is [tex]x^{2} -21x[/tex]
We need to determine the number that is added to the polynomial to complete the square.
The last term of the polynomial can be determined by dividing the term 21 by 2 and then squaring the term.
Thus, we have,
Last term = [tex]\frac{21}{2}[/tex]
Now, squaring the term, we have,
Last term = [tex](\frac{21}{2})^2=\frac{441}{4}[/tex]
Thus, the number added to the polynomial by completing the square is [tex]\frac{441}{4}[/tex]
