Help

[whytehaze]

I got my test back, and got these wrong and I don't know the right answers to these...

Find the derivatives of the following functions:
1. (x^3-2)4^x
2. Axe^(Bx) + C
3. (x^2)/(3x-4)
4. (e^2x)/?(5x+2)
5. (1)/(x^3-5x+6)

 

[mmm4444bot]

Hello Haze:

Please show your work and results.

Then we'll be able to see why you got them wrong. This, in turn, will allow us to see how best to help you.

Cheers,

~ Mark

 

[galactus]

I will show you number 5. Anytime you can use the product rule over the quotient rule it is a good idea.

You can rewrite #5.

$\displaystyle \frac{1}{x^{3}-5x+6}=(x^{3}-5x+6)^{-1}$

Now, all we need is the chain rule. $\displaystyle (-1)(x^{3}-5x+6)^{-2}(3x^{2}-5)$.

Now, simplify and tidy up.

Now, the same thing with the quotient rule.

$\displaystyle \frac{(x^{3}-5x+6)(0)-1(3x^{2}-5)}{(x^{3}-5x+6)^{2}}$

Now, tidy up and you should have the same as the above method.

 

[whytehaze]

Hey guys, do you think that you could help me with #4? My tutor helped me with all the rest, but he wasn't sure of the 4th one. Thanks.