Question

Find the derivative of f(x) = -4x2 + 11x at x = 10.

a) 19.5
b) -69
c) 30
d) -300

Answer 1

b

Explanation:

Using the power rule to differentiate each term

Given

f(x) = - 4x² + 11x , then

f'(x) = - 8x + 11

At x = 10

f'(10) = - 8(10) + 11 = - 80 + 11 = - 69 → b

Answer 2

-69 (Answer b)

Explanation:

Apply the power rule for differentiation:

(d/dx){-4x^2 + 11x} = -8x + 11

Now substute 10 for x:

f '(x) = -8(10) + 11 = -80 + 11 = -69 (Answer b)