f(x) = 3x +1
a) f(9) - f(1)
f(9) = 3.9 + 1 = 10
f(1) = 3.1 + 1 = 4
10 - 4 = 6
________________
b) f(4) - f(-2)
3.4 + 1 - 3.(-2) + 1 = 13 - (-5) = 13 + 5 = 18
________________
c) f(-5) + f(3)
3.(-5) + 1 + 3.3 + 1 = -15 + 11 = -4
________________
d) f(2) + f(6)
3.2 + 1 + 3.6 + 1 = 6 + 2 + 18 = 26
________________
e) f(10) + f(3)
3.10 + 1 + 3.3 + 1 = 30 + 11 = 41
