Help me please?

x^2 + 2x + 13 = -8
Answer choice:
B. Add 8 to both sides

8 ounces per cup
120 ounces × (1 cup)/(8 ounces) = 15 cups

It depends on your solution method of choice.

If you intend to use the quadratic formula, it is appropriate to add 8 to both sides. (This is the most general, but not necessarily the fastest or easiest.)

If you intend to solve it by completing the square, it is appropriate to subtract 13 (or 12) from both sides.

x^2 + 2x + 13 = -8
x^2 + 2x + 1 = -20 ... subtract 12. This makes the left side equal to (x+1)^2
x+1 = ±√-20 ... take the square root
x = -1 ± i*2√5 ... add -1

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The first step is always "look at what you have and what you want, then formulate a strategy". Here, that look will tell you the equation is easily solved by completing the square.

Add 8 to both sides so that the RHS is zero

You'll want to put this into standard form, which is:

ax² + bx + c = 0

So the first step is to add 8 to both sides (option B)