Find the Perfect Square Trinomial x^2-21x

$x^{2} - 21 x$

Step 1

To find the $c$ value $c = {(\frac{b}{2})}^{2}$ , divide the coefficient of $x$ by $2$ and square the result.

Use the power rule ${(a b)}^{n} = a^{n} b^{n}$ to distribute the exponent.

Apply the product rule to $- \frac{21}{2}$ .

${(- 1)}^{2} {(\frac{21}{2})}^{2}$

Apply the product rule to $\frac{21}{2}$ .

${(- 1)}^{2} \frac{21^{2}}{2^{2}}$

Raise $- 1$ to the power of $2$ .

$1 \frac{21^{2}}{2^{2}}$

Multiply $\frac{21^{2}}{2^{2}}$ by $1$ .

$\frac{21^{2}}{2^{2}}$

Raise $21$ to the power of $2$ .

$\frac{441}{2^{2}}$

Raise $2$ to the power of $2$ .

$\frac{441}{4}$

Step 2

Add $\frac{441}{4}$ to get the perfect square trinomial.

$x^{2} - 21 x + \frac{441}{4}$