lkhulkjh

Question

lkhulkjh

anonymous · Answer

@robtobey @tkhunny @Callisto @Abhisar @asnaseer @Luigi0210 @Loser66

anonymous · Answer

i get that the formula for linearization is f(a)+f'(a)(x-a) but what would a be?

asnaseer · Answer

ok - looks like you have the correct formula there - where are you stuck?

anonymous · Answer

what do i use for a? the function needs to be in terms of x

asnaseer · Answer

the linearization of a function $f(x)$ at $x=a$ is given by:$$y=f(a)+f'(a)(x-a)$$now, what does your question ask you to calculate? you should be able to work out what 'a' should be.

anonymous · Answer

so i just use -2 for a? if i do that i get -40x-108 which is wrong

asnaseer · Answer

what did you get for $f'(x)$?

anonymous · Answer

4x^3+4x

asnaseer · Answer

that is correct

anonymous · Answer

so what am i doing wrong?

asnaseer · Answer

please show all your steps so that I can help spot where you may have made a mistake

asnaseer · Answer

actually I get the same answer

asnaseer · Answer

what do you believe the answer /should/ be?

anonymous · Answer

ok. f(a)=28 f'(a)=-40 x-a=x+2  
therefore, L(x)=28-40(x+2)=-40x-108

anonymous · Answer

i believe the answer should be -40x-108

asnaseer · Answer

??? - then your answer IS correct :)

anonymous · Answer

but its not

asnaseer · Answer

what is the answer /claiming/ to be?

anonymous · Answer

its online hw. they tell you if you are right or wrong. they dont give you the answer

asnaseer · Answer

hang on - just spotted a subtle error...

asnaseer · Answer

$$L(x)=28-40(x+2)=28-40x-80=-52-40x$$

asnaseer · Answer

I /think/ we both made the same mistake of treating the $28$ as $-28$ :)

anonymous · Answer

oohh ok.  thanks haha

asnaseer · Answer

yw :)

I guess being human means you will make mistakes :)