Question

@Noura11

Answer 1

@dan815

Answer 2

WE have :
\[(9n^7-8n^4+2n^2+2)+(9n^5+4n^4-3n)=9n^7+9n^5+(\color{red}{-8n^4+4n^4})+2n^2-3n+2\\
=9n^7+9n^5-4n^4+2n^2-3n+2 \]

Answer 3

thats it?

Answer 4

Of course it is !

Answer 5

add the like terms