find the derivative of x^(2) +3x -5 using the definition of the derivative (i.e.) using limits

Question

anonymous · Answer

i guess my explanation was not good, but if you have a question i would be happy to answer it

laddiusmaximus · Answer

satellite73 your explanation made sense except for one part.

laddiusmaximus · Answer

why does (x + h)^(2) become x^(2) 2xh?

anonymous · Answer

i hope that is not what i wrote

laddiusmaximus · Answer

(x+h)^(2)-3(x+h) -5  becomes what?

anonymous · Answer

$$(x+h)^2=(x+h)(x+h)=x^2+2xh+h^2$$

laddiusmaximus · Answer

crap!!! I didnt think to look at it like that!!

laddiusmaximus · Answer

FOIL

anonymous · Answer

and so 
$$(x+h)^2+3(x+h)-5=x^2+2xh+h^2+3x+3h-5$$ by the distributive law

laddiusmaximus · Answer

i was thinking x^(2) + h^(2)

anonymous · Answer

attachment

anonymous · Answer

it is the distributive law
foil is a trick math teachers play on students

laddiusmaximus · Answer

well thats not cool

laddiusmaximus · Answer

one more thing. why is it +3(x+h) and not -3(x+h)?

anonymous · Answer

because you wrote 
$$f(x)=x^2+3x-5$$ that is why it is + and not -

laddiusmaximus · Answer

i guess im too literal when I try to plug it into f(x) (x+h)-f(x)/h