Question

What number must you add to the polynomial below to complete the square? x^2-21x

Answer 1

The number added to the polynomial is $\frac{441}{4}$

Explanation:

The given polynomial is $x^{2} -21x$

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 = $\frac{21}{2}$

Now, squaring the term, we have,

Last term = $(\frac{21}{2})^2=\frac{441}{4}$

Thus, the number added to the polynomial by completing the square is $\frac{441}{4}$