Complete the steps of derivation of the quadratic formula

Step 1. We are going to begin with standard form a quadratic equation: 

Step 2.  Divide both sides of the equation by :




Step 3. Subtract  from both sides of the equation:



Step 4. Complete the square of the left hand side by adding  to both sides:



Step 5. Take square root to both sides of the equation:



Step 6. Subtract  from both sides of the equation:



Step 7. Simplify the radicand of the left hand side of the equation:





Step 8. Take  outside the radical:



Step 9. Combine the two fractions and rearrange the terms in the radical: 

The correct answer is 7