Question 1007391
{{{ g(x) = x^2 + 10x - 39 }}}
You can set {{{ g(x) = 0 }}} and 
complete the square
{{{ x^2 + 10x - 39 = 0 }}}
{{{ x^2 + 10x = 39  }}}
{{{ x^2 + 10x + ( 10/2 )^2 = 39 + ( 10/2 )^2 }}}
{{{ x^2 + 10x + 25 = 39 + 25 }}}
{{{ x^2 + 10x + 25 = 64 }}}
{{{ ( x + 5 )^2 = 8^2 }}}
{{{ x + 5 = 8 }}}
{{{ x = 3 }}}
and also:
{{{ x + 5 = -8 }}}
{{{ x = -13 }}}
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So, the factors are:
{{{ g(x) = ( x - 3 )*( x + 13 ) }}}