Question

Consider the function f(x) = x² – 3x – 4 and complete parts (a) through (C). (a) Find f(a+h); f(a+h)-f(a) (b) Find (c) Find the instantaneous rate of change of f when a = 7. (a) f(a+h) = (Simplify your answer. Do not factor.)

Answer 1

Answer:

(a)

$f(a+h)=a^{2} +2ah+h^{2} -3a-3h-4$

(b)

$f(a+h)-f(a)=2ah+h^{2} -3h$

(c)

$\frac{df(a+h)}{dx} \left \{ { \atop {a=7}} \right. =2h+11$

Step-by-step explanation:

(a)

Simply evaluate (a+h) in the function:

$f(a+h)=(a+h)^{2} -3(a+h)-4=a^{2} +2ah+h^{2} -3a-3h-4$

(b)

Evaluate (a) in the function:

$f(a)=a^{2} -3a-4$

Using the previous answers lets calculate f(a+h)-f(a)

$f(a+h)-f(a)=a^{2} +2ah+h^{2} -3a-3h-4-(a^{2} -3a-4)=2ah+h^{2} -3h$

(c) To find the rate of change of f(a+1) when a=7 we need to calculate its derivate at that point:

$\frac{df(a+h)}{dx} \left \{ { \atop {a=7}} \right. =2a+2h-3=2(7)+2h-3=2h+14-3=2h+11$