## Christos 3 years ago Limits, Can you help me out with this please: http://screencast.com/t/lLsaUJErdX

1. anonymous

$f(x)=2x^3+1$ $f'(x)=3x^2$ $f'(-1)=3$

2. Christos

dude f'(x) = 6x^2

3. Christos

@satellite73

4. anonymous

oh right

5. anonymous

so $$f'(-1)=6$$ is the slope

6. Christos

I know the slope, the rest is what I dont know

7. anonymous

you have the slope and the point use the point - slope formula

8. anonymous

slope is $$6$$ and the point is $$(-1,-2)$$

9. anonymous

oops $$(-1,-1)$$

10. Christos

You see, I already have the solution. But I believe it's wrong http://screencast.com/t/2tjXXmjz9 That's why I asked you guys to cross over it

11. anonymous

$y+1=6(x+1)$

12. Christos

Is this wrong like I believe http://screencast.com/t/2tjXXmjz9 ?

13. anonymous

yeah that is wrong for sure

14. Christos

ty god

15. Christos

I knew it

16. anonymous

yes a=1 and not -1

17. anonymous

$f(-1)=2\times (-1)^2+1=-2+1=-1$

18. Christos

ty

19. anonymous

and f(a) =2

20. anonymous

its just wrong don't waste time thinking about it

21. Christos

My final result y = 6x + 7

22. anonymous

no y=6x+1

23. Christos

Kinda why

24. Christos