Answer:
Third Choice:
[tex] x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a} [/tex]
Step-by-step explanation:
One line has
[tex] x + \dfrac{b}{2a} = \pm \dfrac{\sqrt{b^2 - 4ac}}{2a} [/tex]
The next line's reason is that b/2a was subtracted from both sides.
The missing line is:
[tex] x = -\dfrac{b}{2a} \pm \dfrac{\sqrt{b^2 - 4ac}}{2a} [/tex]
Then it simplifies to
[tex]x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a}[/tex]
