Question

find the derivative of -6/x when x=12..help please...

Answer 1

you are given a process to work out .. what have you got?

Answer 2

ok,
(-6/(x+h)-(6/x))/h

Answer 3

youve dropped a negative

Answer 4

ah so
((-6/(x+h)-(-6/x))/h

Answer 5

common denom. so:-6x^2-6xh+6x^2+6xh
now that's the part I'm confused about

Answer 6

(-6/(x+h)--6/x)/h

(-6x/x(x+h)+ 6(x+h)/x(x+h))/h

( (-6x+6x+6h)/x(x+h) )/h

( (6h)/x(x+h) )/h

6h/hx(x+h)

6/x(x+h)

Answer 7

\[\lim_0~\dfrac{\dfrac{-6}{x+h}-\dfrac{-6}{x}}{h}\]
\[\lim_0~\dfrac{\dfrac{-6x+6(x+h)}{x(x+h)}}{h}\]
\[\lim_0~\dfrac{-6x+6(x+h){}}{hx(x+h)}\]
\[\lim_0~\dfrac{\cancel{-6x+6x}+6h{}}{hx(x+h)}\]
\[\lim_0~\dfrac{6\cancel{h}{}}{\cancel{h}x(x+h)}\to \frac{6}{x(x+0)}\]

Answer 8

let x=12 :)

Answer 9

I see it, Thank you very much :DD

Answer 10

youre welcome

Answer 11

do you mind helping me on another derivative question?

Answer 12

f(x)=5x+9 x=2

Answer 13

@amistre64

Answer 14

i got
(5(x+h)+9)-(5x+9)/h
5x+5h+9-5x-9/h

Answer 15

the slope of a line is constant ... regardless of any point in the line

Answer 16

you did fine so far now subtract what gets subtracted

Answer 17

thank you, so it would be just be 5 then..

Answer 18

yes

Answer 19

thank you soo much :DD i think i got this now

Answer 20

practice helps ;)