Suggestion

The equation in \(x\), \[3x^4 - 16x^3 +18x^2 + k = 0\] has four real solutions

  1. when \(-27 < k < 5\);
  2. when \(5< k <27\);
  3. when \(-27< k <-5\);
  4. when \(-5< k <0\).

The curve is the function \(y = 3x^4 - 16x^3 +18x^2 + k\).