## anonymous one year ago {[3(x+h)^2 +(x+h)]- (3x^2+x)} / h

1. anonymous

$\frac{ [3(x+h)^{2}+(x+h)]-(3x ^{2}+x) }{ h }$

2. Vocaloid

hint: use foil to expand (x+h)^2

3. anonymous

Ive expanded it and tried to solve it but my answer is not a choice on my homework

4. Vocaloid

what did you get as the answer? you may have made a simple math error somewhere

5. anonymous

i think the problem is my division after i distribute and cancel out like terms i get (6xh+3h^2+h)/h i get 6x +8h at the end

6. Vocaloid

not quite, h should not be in the final answer at all. let's start from the beginning, ok?

7. Vocaloid

|dw:1443578057830:dw|

8. Vocaloid

|dw:1443578094689:dw|

9. anonymous

okay so then it would be [3(x^2 + 2xh +h^2 ) + x+h -3x^2 -x]/h

10. anonymous

alright so far so good

11. Vocaloid

then we use distribution to expand the numerator|dw:1443578189706:dw|

12. Vocaloid

then we cancel out terms|dw:1443578230609:dw|

13. anonymous

i have a question does 3 not distribute to h^2 = 3h^2 ?

14. Vocaloid

whoops

15. Vocaloid

|dw:1443578317416:dw| (and I made a small mistake earlier, h should be in the answer. I was thinking of derivatives for some reason)

16. Vocaloid

now, we factor out h from the numerator|dw:1443578421397:dw|

17. Vocaloid

|dw:1443578448565:dw|

18. anonymous

yeah this is actually trying to solve for a derivative using [f (x+h)- f(x)] / [(x+h)-x]

19. Vocaloid

right, so if we're going for a derivative, all we need to do now is set h = 0

20. anonymous

ohh so i have to factor out the 'h' okay and then the 0

21. Vocaloid

|dw:1443578553000:dw|

22. Vocaloid

so the derivative of 3x^2 + x = 6x + 1

23. anonymous

Yessss this is an answer! thank you i have been trying to solve this for a while. thanks