Question 152616
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You don't have the formula right:

The solution to

{{{ax^2+bx+c=0}}}

is

{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}


Your problem is 

{{{9x^2 - 12x - 4 = 0}}}

{{{a=9}}}, {{{b=-12}}}, {{{c=-4}}}

{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}

{{{x = (-(-12) +- sqrt((-12)^2-4*(9)*(-4)))/(2*(9)) }}}

{{{x = (12 +- sqrt(144+144))/(2*(9)) }}}
 
{{{x = (12 +- sqrt(288))/18 }}}

{{{x = (12 +- sqrt(144*2))/18 }}}

{{{x = (12 +- sqrt(144)sqrt(2))/18 }}}

{{{x = (12 +- 12sqrt(2))/18 }}}

Factor 12 out of the top

{{{x = 12(1 +- sqrt(2))/18 }}}

Divide 12 and 18 by 6

{{{x = 2(1 +- sqrt(2))/3 }}}

That is equivalent to your answers:

Edwin</pre>