If f(x)=9-2|x + 21, find f(-7).
Answer: -1
Same thing as the other question that I helped you with:
Substitute -7 for x
f(-7) = 9-2|-7+2|
Treat the absolute value like parenthesis, and follow the rules of PEMDAS
9-2|-5|
9-2*5
9-10
-1