Question 1877
{{{3x^2 - 18x = -28}}}
{{{x^2 - 6x = -(28/3)}}}

now 2a = 6, so a=3, and a^2 = 9

Adding 9 to both sides, means that the LHS is now the correct form to factorise
{{{x^2 - 6x + 9 = -(28/3) + 9}}}
{{{(x-3)^2 = -(1/3)}}}
{{{(x-3)}}} = +- {{{sqrt(-1/3)}}} which has no real solution. Therefore enter Complex numbers...
{{{x-3}}} = +- {{{(sqrt(1/3))i}}}
{{{x = 3 +- (sqrt(1/3))i}}}

cheers
Jon.