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

When factoring
x² - 4x + 4 = 20,
what goes in the blank?
(x - __ )² = 20

• 4
• 2
• 8
• 20

What value of c would make this a perfect sqaure trinomial?
x² +8x + c

• 4
• 16
• 64
• -16

Complete the Square
x² + 6x = 5

• (x + 3)² = 5
• (x + 6)² = 9
• (x + 3)² = 14
• (x + 6)² = 14

Solve by completing the square.
y² + 10y = -9

• 1 and -12
• -1 and -9
• 1 and -9
• 1 and -1

Find the value of "c" that completes the square.

 $a^2-22a+c$  

• -121

• 121

• 11

• -11

Find the value of "c" that completes the square.

 $k^2-18k+c$  

Solve by completing the square.
 $x^2-8x-20=0$  

•  $x=\left\{-2,\ 10\right\}$  

•  $x=\left\{-10,\ 2\right\}$  

•  $x=\left\{-20,\ -8\right\}$  

•  $x=\left\{8,\ 20\right\}$  

Solve by completing the square.
 $x^2-12x+20=0$  

•  $x=\left\{2,\ 10\right\}$  

•  $x=\left\{-10,\ -2\right\}$  

•  $x=\left\{-12,\ 20\right\}$  

•  $x=\left\{12,\ 20\right\}$  

Solve by completing the square.
 $x^2-14x-15=0$  

•  $x=\left\{1,\ 15\right\}$  

•  $x=\left\{-15,\ -1\right\}$  

•  $x=\left\{-15,\ 1\right\}$  

•  $x=\left\{-1,\ 15\right\}$