a. f(x) = x*x

b. f(x) = x + 1

c. f(x) = sq. root of x

d. f(x) = 2/x

e. f(x) = -3x

We can find the answer by replacing the value of x by a, b & (a+b)

a. (a+b)*(a+b) != a*a + b*b

b. a + b + 1 != a + 1 + b + 1

c. sqrt(a+b) != sqrt(a) + sqrt(b)

d. 2/(a+b) != 2/a + 2/b

e. -3(a+b) = -3a - 3b (TRUE)

Hence the answer is option E