Question 258195
Remove the parentheses that are not needed from the expression. 

3f^2+5f-9+4f^2-7f+12

Since 3f^2 and 4f^2 are like terms, add 4f^2 to 3f^2 to get 7f^2.

7f^2+5f-9-7f+12

Since 5f and -7f are like terms, add -7f to 5f to get -2f. 

7f^2-2f-9+12

Add 12 to -9 to get 3. 

Answer:  7f^2-2f+3