Solve the equation by completing the square

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Solve the equation by completing the square: 3x² - 3 = -12x. Show all of your work

Jul 18th, 2015

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$\\ 3x^2-3=-12x\\ \\ 3x^2+12x-3=0\\ \\ 3(x^2+4x-1)=0\\ \\ x^2+4x-1=0\\ \\ x^2+4x=1\\ \\$

To complete the square

i) Take half of coefficient of x term which gives 4/2 = 2

ii) Square it which gives 2^2 = 4

iii) Add 4 to both sides of the equation

$\\ x^2+4x+4=1+4\\ \\ (x+2)^2=5\\ \\$

$\\ x+2=\pm\sqrt{5}\\ \\ x=-2\pm\sqrt{5}$

So, solution is $x=-2\pm\sqrt{5}$

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Jul 18th, 2015

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Jul 18th, 2015
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Jul 18th, 2015
Oct 24th, 2016
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