3. If f(x) = 3x2 + x + 1 and g(x) = x2 + 5x + 3, what is (f+g)(x) equal to?
a. 4x2 + 5x + 4 b. 4x2 + 6x + 4
c. 3x2 + 5x + 4 d. 3x2 + 6x + 4​