I am down to three I can not figure out, help please.

subtract
(2x^4 + 9x^3 -1) - (9x^2 -2x +4)=

( 2X^4 + 9X^3 -1 ) - ( 9X^2 -2X + 4 ) To remove a parenthesis with a negative sign out front, change the

sign of each term within the pa-
renthesis:
2X^4 + 9X^3 -1 -9X^2 + 2X -4
Combine like-terms:
2X^4 + 9X^3 -9X^2 +2X -5.
There were only two like-terms (-1 and -4 ); i don't believe this
can be simplified further.