Here is one way an expression in standard form is rewritten into vertex form.
\(\begin{align}&x^2 - 7x + 6 &\qquad &\text{original expression}\\ &x^2 - 7x + \left(\text-\frac72\right)^2 + 6 -\left(\text- \frac72\right)^2 &\quad&\text{step 1} \\ &\left(x-\frac72\right)^2 + 6-\frac{49}{4} &\quad&\text{step 2}\\ &\left(x-\frac72\right)^2 + \frac{24}{4}-\frac{49}{4} &\quad&\text{step 3}\\ &\left(x-\frac72\right)^2-\frac{25}{4} &\quad&\text{step 4} \end{align}\)
- In step 1, where does the number \(\text-\frac72\) come from?
- In step 1, why is \(\left(\text-\frac72\right)^2\) added and then subtracted?
- What happens in step 2?
- What happens in step 3?
- What does the last expression tell us about the graph of a function defined by this expression?