Please HELP with this function question?

Question

For f(x) = 7x^3 – 3x^2 + 9x – 11, evaluate f" (2/3)

a) 43/3
b) 22
c) -11
d) 2/3

Answer 1

differentiate
21x^2 -6x +9
substitute 2/3 for x
21(4/9) -6(2/3) +9=
28/3 -12/3 +9=
16/3 +9=
16/3 + 27/3 = 43/3 The answer is a)

Answer 2

First thing to do is get the first derivative, f'(x).

f'(x) = 21x^2 - 6x +9

Second thing to do is get the second derivative, f"(x)

f"(x) = 42x - 6

since you are being asked to evaluate f"(x) when x = 2/3, then plug in 2/3 in the equation for f"(x)

f"(2/3) = 42 * (2/3) -6

f"(2/3) = 28 - 6

f"(2/3) = 22

answer is b

Answer 3

b) 22