Question 981418
{{{3x^2 +2x- 4 = 0}}}....use quadratic formula

{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} ....in your case, {{{a=3}}},{{{b=2}}}, and {{{c=-4}}}

{{{x = (-2 +- sqrt( 2^2-4*3*(-4) ))/(2*a) }}} 

{{{x = (-2 +- sqrt( 4+48 ))/(2*3) }}}

{{{x = (-2 +- sqrt( 52 ))/6 }}}

{{{x = (-2 +- sqrt( 4*13 ))/6 }}}

{{{x = (-2 +- 2sqrt( 13 ))/6 }}}

{{{x = (-cross(2)1 +- cross(2)1sqrt( 13 ))/cross(6)3 }}}

{{{x = (-1 +- sqrt( 13 ))/3 }}}

solutions:

exact:
{{{x = (-1 + sqrt( 13 ))/3 }}}

{{{x = (-1 - sqrt( 13 ))/3 }}}

approximate:

{{{x = (-1 + 3.61)/3 }}}=>{{{x = 0.87}}}

{{{x = (-1 - 3.61)/3 }}}=>{{{x = -1.54}}}