Quadratic Equation by Completing the Square

What is the first step to solving THIS equation by completing the square?
a² + 10a + 21 = 0

• Set the equation equal to zero

• Divide 10 by 2 and add the result to both sides

• Add a² and 10a together

• Subtract the 21

Solve the following quadratics equation by completing the square...

x² - 10x - 5 = 0

• x = -5 ± √30

• x = 5 ± √30

• x = 30 ± √5

• x = -30 ± √5

Solve the following quadratics equation by completing the square... x^2 + 6x - 3 = 0

Complete the square for: v² - 18v + 87 = 7

• (v + 9)² - 1

• (v + 9)² + 1

• (v - 9)² - 1

• (v - 9)² + 1

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• A
• B
• C
• D

Lori is completing the square to solve the quadratic equation. Which equation is the result of correctly completing the square?​