Respuesta :

like terms are similar in exponents.
12x^2 can be combined with -3x^2
9x^3 with -5x^3
-8x^4 is on its own
Final=
-8x^4 + 4x^3 + 4x^2
The like terms have the same degree. 
Answer 
-8x⁴ + 4x³ + 4x²