Question 146143
Er...not quite right!
Your first step is ok, but that leaves you with the sum of squares binomial which does not have real factors.
However, is that a negative sign in front of the {{{3x^2}}}?, if it is, then you can factor as follows:
{{{-3x^2+243 = -3(x^2-81)}}}={{{-3(x+9)(x-9)}}}
When you factor the sum of squares binomial {{{x^2+81)}}} you get {{{(x+9i)(x-9i)}}} where: {{{i = sqrt(-1)}}}