## mathcalculus 2 years ago derivatives: = (4x+4)^-3 find f' (x) and f'(4)

1. camoJAX

you have to use the chain rule

2. mathcalculus

yes, can we begin to how to use the chain rule?

3. clickspiker23

if i am correct it would be -3(4x+4)^-4 * 4 would be the derivative. and then plug in 4 to the equation

4. areyes06

in order to use the chain rule you must start with power rule by multiplying (4x+4) by the power of -3 then reduce power by 1 next the expression but multiplied by the derivative of whats inside that being the 4x+4 the derivative of that is 4 . after doing that you get the expression @clickspiker23 has posted and to finish the problem you solve the equation by plugging in 4 for x does this help and explain the chain rule more. you do deriv of the outside in this case using power rule times the deriv of whats inside.

5. SinginDaCalc2Blues

Hi...if you want a really dumed down explanation of the chain rule, listen to this... If you hold a chain up in the air and dangle it, the bottom link relies on the link above it, and the link above that relies on the next one up, and so on... Remember the acronym PEMDAS ? Parenthesis, Exponents, Multiplication, Division, Addition, Subtraction ? Well the P is more powerful than the E, and the E is more powerful than the M and so on...kinda like a Chain... In your problem, (4x+4)^-3 , the big bully would be the -3, and the bully is standing on top of the poor kid named (4x+4), so if you think of it that way, deal with the exponent first...bring that dirty bully down in front, leave the poor kid in the box alone, then take 1 away from what used to be the exponent...then after the bully was taken care of, let the poor beat up kid outta the box and work his derivative which would be 4...all that gets separated and multiplied together... One thing to note however, unlike PEMDAS where you absolutely had to do P before E and so on, you could actually do the chain rule in reverse... You could actually let the poor beat up kid outta the box first, then take care of the bully...this is okay to do because everything is multiplied together in the end and the answser works out to be the same!!! See my picture for clarity...HOPE THIS HELPS!!! GOOD LUCK!

6. SinginDaCalc2Blues

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7. SinginDaCalc2Blues

If the above picture got cut off, just click on 7.bmp Hope this helps clear things up!

8. camoJAX

Nice way to dumb down the chain rule

9. SinginDaCalc2Blues

Thanks...I just hope it helps!