add (2+9x^3+7x^5-4x^4)+(6x^4-3x^3+2+9x^5)

(2 + 9x³ + 7x⁵ - 4x⁴) + (6x⁴ - 3x³ + 2 + 9x⁵)

Rearrage, placing like terms together:

(7x⁵ + 9x⁵) + (-4x⁴ + 6x⁴) + (9x³ - 3x³) + (2 + 2)

Simplify these terms:

16x⁵ + 2x⁴ + 6x³ + 4