1. ## differentation

hi,

i nned to know how to differentiate this;

y=3x^2-4x+1

i have dy/dx= -9x^-4+8x+1

would this be correct or would i not keep the +1 on the end?

thanks!

2. ## Re: differentation

Is this the function you have to differentiate:
$y=3x^2-4x+1$
?

Maybe you should split up in terms and calculate the derivative of each term.
Do you know the derivative of a constant number? ...
Do you know this rule:
$D(x^n)=n\cdot x^{n-1}$? ...

3. ## Re: differentation

basically what i did was:
3x^-3=-9x^-4, times the 3 and -3 together and take away one power
same with 4 and 2, times them to get 8 and take away one power to get 8x.

so now i have dy/dx= -9x^-4+8x but i don't know if i keep the +1 or not?

4. ## Re: differentation

I can't follow why you're calculating derivatives like that.
Do you understand that:
$\frac{d(3x^2)}{dx}=6x$
?

5. ## Re: differentation

no i don't understand, im just going by what my teacher has told us and how i have done them before.

6. ## Re: differentation

Ok, no problem we will figure it out.
How would you calculate:
$\frac{d(3x^2)}{dx}= ...$
?

7. ## Re: differentation

i don't know.

8. ## Re: differentation

Maybe you should talk with your teacher about this and take soms lessons, because I think it's really difficult to explain everything about calculating derivatives via the pc.
What have you learned yet at school about derivatives? ...

9. ## Re: differentation

we have basically learn what i have done to sole the question, but i was unsure if it was correct. i will try and see her soon to discuss it! thanks for the help anyway though!

10. ## Re: differentation

You're welcome and it's looks indeed a good idea to go to your teacher .

11. ## Re: differentation

Originally Posted by andyboy179
i don't know.
The formula given at the end of post #2 (and which will undoubtedly be in your class notes and textbook) tells you exactly how to do it.