Daily Regents: Completing the Square (August 2014)

I'll be reviewing a New York State Regents Exam Question every day from now until the Regents exams begin next month. At least, that is the plan.

August 2014, Questions 32

32. A student was given the equation x² + 6x - 13 = 0 to solve by completing the square. The first step that was written is shown below.

x² + 6x = 13
The next step in the student’s process was x² + 6x + c = 13 + c
State the value of c that creates a perfect square trinomial.
Explain how the value of c is determined.

To complete the square, you have to take one-half of the "b" term, which is 6. That gives you 3. Then you have to square the 3, which gives you 9.
Therefore, c = 9.

(x + 3)² = x² + 6x + 9

Any questions?

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