Thread: f(x) = -x^3 evaluating for f(a+h)

When I evaluate f(x)= -x^3 for f(a+h)

How is it suppose to look? I'm not sure what to do with the negative in front of the x

f(a+h) = -[(a+h)(a+h)(a+h)]

or

f(a+h) = [(-a-h)(-a-h)(-a-h)]

Originally Posted by superduper1

When I evaluate f(x)= -x^3 for f(a+h)

How is it suppose to look? I'm not sure what to do with the negative in front of the x

f(a+h) = -[(a+h)(a+h)(a+h)]

or

f(a+h) = [(-a-h)(-a-h)(-a-h)]

means:



so here you want:




CB

I'm not sure what I'm doing wrong. The answer I get is incorrect.
f(x) = -x^3
evaluate for f(a+h)-f(a) / h

f-(x^3)= -a^3-3a^3h-3ah^2-h^3
Then when I evaluate for f(a) I get:
f(a) = -a^3

After the -a^3 subtract each other out...I factor out an h from the numerator to cancel out an h from the denominator and get:
-3a^3 - 3ah-h^2

Originally Posted by superduper1

I'm not sure what I'm doing wrong. The answer I get is incorrect.
f(x) = -x^3
evaluate for f(a+h)-f(a) / h

f-(x^3)= -a^3-3a^3h-3ah^2-h^3
Then when I evaluate for f(a) I get:
f(a) = -a^3

After the -a^3 subtract each other out...I factor out an h from the numerator to cancel out an h from the denominator and get:
-3a^3 - 3ah-h^2

You should get:



just check your algebra.

CB

Originally Posted by superduper1

I'm not sure what I'm doing wrong. The answer I get is incorrect.
f(x) = -x^3
evaluate for f(a+h)-f(a) / h

f-(x^3)= -a^3-3a^3h-3ah^2-h^3

Probably a typo. The second term should be "-3a^2h", not "-3a^3h".

Then when I evaluate for f(a) I get:
f(a) = -a^3

After the -a^3 subtract each other out...I factor out an h from the numerator to cancel out an h from the denominator and get:
-3a^3 - 3ah-h^2

you continued your typo- this should be -3a^2- 3ah- h^2