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Solve the quadratic equation below by completing the square.4n2-16n-21=44

 Apr 13, 2016
 #1
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Solve for n over the real numbers:
4 n^2-16 n-21 = 44

Divide both sides by 4:
n^2-4 n-21/4 = 11

Add 21/4 to both sides:
n^2-4 n = 65/4

Add 4 to both sides:
n^2-4 n+4 = 81/4

Write the left hand side as a square:
(n-2)^2 = 81/4

Take the square root of both sides:
n-2 = 9/2 or n-2 = -9/2

Add 2 to both sides:
n = 13/2 or n-2 = -9/2

Add 2 to both sides:
Answer: |  n = 13/2              or              n = -5/2

 Apr 13, 2016
 #2
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 Apr 13, 2016
edited by MaxWong  Apr 13, 2016

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