**4x**^{3} – [9x^{2} – { -5x^{3} – (7 + 7x^{2}) + 6x}}

= 4x^{2} – [9x^{2} – { -5 -2 + 7×2 + 6x}]

= 4x^{3} – [9x^{2} + 5x^{3} + 2 – 7x^{2} – 6x]

= 4x^{3} – 9x^{2} – 5x^{3} – 2 + 7x^{2} + 6x

= 4x^{3} – 5x^{3} – 9x^{2} + 7x^{2} + 6x – 2

= -x^{3} – 2x^{2} + 6x – 2