Question 690214
Divide the entire equation by .1
{{{x^2 - 2x - 9 = 0}}}
Move the 9 to the other side
{{{x^2 - 2x = 9}}}
Take {{{1/2}}} of the x coefficient and square it:  {{{((1/2)b)^2}}}
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b came from {{{ax^2+bx+c=0}}}
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{{{(1/2)2 = 1^2 = 1}}}
Add 1 to both sides
{{{x^2 - 2x + 1 = 9 + 1}}}
{{{(x-1)^2 = 10}}}
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{{{sqrt(x-1)^2}}} = +/- {{{sqrt(10)}}}
x-1 = +/-{{{sqrt(10)}}}
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{{{x=1+-sqrt(10)}}}
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{{{highlight_green(x=1+sqrt(10))}}} and {{{highlight_green(x=1-sqrt(10))}}}