Explicação passo-a-passo:
A) (3x²+5x-9)+(4²-5x-7)=
3x²+5x-9+4x²-5x-7
7x²-5x+5x-7
7x²+2
B) (8a²-5a+3)-(4a²-2a-4)=
8a²-5a+3-4a²-2a²+4
4a²-2a²-5a+3-4
2a²-5a-1
C) (6x+3)+(9x+8)=
6x+3+9x+8
6x+9x+8-3
15x+5
D) (104x²+72x-56)+(32x²-109x-17)
104x²+72x-56+109-17
208²+50-17
208²+33
