Question

Find the derivative of f(x) = 8/x at x = -1.
the answer choices are: 4,0,8,-8

Answer 1

Since I can't just tell you what the answer is, I will tell you what it is not. It is not 4, o, or 8.

Answer 2

0*

Answer 3

d/dx (8/x) = 8 x d/dx(1/x) = 8/x^2
substitute the value of x
we get 8/-1 = -8

Answer 4

thanks! @Niall , and ok so to find the derivative, you just plug in x? @paul1231

Answer 5

Could you help me with one more? @Niall @paul1231 Find the derivative of f(x) = -6/x at x = 12. Answer Choices: 24,1/2,1/24,2

Answer 6

what is the derivative of 1/x?

Answer 7

im not sure... how can i find it? @paul1231

Answer 8

do you know the derivative of x?

Answer 9

no...i really have no clue how to do this, im not really sure what the 'derivative' is @paul1231

Answer 10

https://www.google.co.in/search?gs_rn=26&gs_ri=psy-ab&tok=jEsYWTlmsIi7TbUXsUtYDg&cp=13&gs_id=1m&xhr=t&q=derivative+formulas&bav=on.2,or.r_qf.&bvm=bv.51773540,d.aGc&biw=1024&bih=677&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=Z6EoUt-dNuXOiAejiIHYDQ#facrc=_&imgdii=_&imgrc=p1jEy_Wb3kpJQM%3A%3BJQ-Yuw8-33Js-M%3Bhttp%253A%252F%252Fwww.sosmath.com%252Ftables%252Fderivative%252Fimg5.gif%3Bhttp%253A%252F%252Fwww.sosmath.com%252Ftables%252Fderivative%252Fderivative.html%3B356%3B591

Answer 11

refer to that and tell me what the derivative of 2x is

Answer 12

d/dx (2x)= 2x/2x^2? @paul1231

Answer 13

2f'(2x) = x^2
f'(2x) = x^2 / 2

Let u = 2x. Then x = u/2, so:

f'(u) = (u/2)^2 / 2 = u^2 / 8

Thus:

f'(x) = x^2 / 8

Answer 14

d/dx(2x) is 2. DAMNIT