The principal square root of a real number can't be negative. That's a little different than saying that the Cubs probably won't win the pennant next year. (Hey, we're just being realistic.)
Whatever 9x + 3 is, its square root will not be -11. This equation has no real number solutions.
Sometimes, after squaring both sides of the equation, we find ourselves with a quadratic equation. This is always good news, because we can plug and chug. Mostly plug, but you can chug as well if you'd like. It's a free country, nobody's stopping you.