Thread: need help with algebra finding derivative
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Old September 7th, 2008, 02:11 PM
stones44 stones44 is offline
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Quote:
Originally Posted by Jhevon View Post
where did 6x come from?

you simplified something wrong. expanding everything, you should get:

\lim_{\Delta x \to 0} \frac {x^3 + 3x^2(\Delta x) + 3x(\Delta x)^2 + (\Delta x)^3 - 3x - 3 \Delta x + 3 - x^3 + 3x - 3}{\Delta x}

now cancel what is to be canceled, simplify as much as possible, and take the limit
doesnt -3(x+Ax) = -3x + -3Ax ? and then the other -3x so -6x
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