How do you solve using the completing the square method x^2 = 2x + 4?

1 Answer
EZ as pi
Oct 26, 2017

x = 3.236" "or" "x=-1.236

Explanation:

In the equation x^2 -2x-4=0, " "-4 is not (b/2)^2

x^2 -2x " "=4" "larrmove -4 to the right side

Add color(blue)((b/2)^2) to both sides color(blue)( ((-2)/2)^2 =1)

x^2 -2x color(blue)(+1)=4color(blue)(+1)

" "(x-1)^2 =5

" "x-1 = +-sqrt5

" "x = +sqrt5+1color(white)(xxxxxx) or x = -sqrt5+1

" "x = +sqrt5+1color(white)(xxxxxx) or x = -sqrt5+1

x = 3.236" "or" "x=-1.236

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