The illegal values of b are when the denominator equals 0.
So, 
gives you (b-4)(b+2)=0
Therefore, b=4 and b=-2, which is answer A.
C would be the answer. When you simplify the equations C does not contain a radical.
METHOD 1
f(3) = 20
f(4) = 30
f(5) = 42
f(6) = 56
rate of change
f(4)-f(3)=10
f(5)-f(4)=12
f(6)-f(5)=14
then the average of change is 10+12+14 /3 = 12
METHOD 2 --- faster
rate of change = f(6)-f(3) / 6-3
= (36+18+2)-(9+9+2) / 3
= 36/3 = 12
3.25 x 25% = .81
3.25- .81 = $2.44
$2.44 is the sale price
120/4=30. Remember its widthxlength. if you forget ask your teacher or look online for more help. Good luck.
