Question

If the graph of f(x)=2x^2+k/x has a point of inflection at x=-1, then the value of k is..

Answer 1

do i find the derivative of f(x) first?

Answer 2

yes so f'(x)= 4x-kx^-2. if it has an inflectionat x=-1 then f'(-1)=0 so 4(-1)-k(-1)^2=0, solve it. :D enoy brah.

Answer 3

at a point of inflection f''=0, not f' so that's not quite right

Answer 4

My bad

Answer 5

so @monkeywall101 what is \(f''(x)\)?

Answer 6

4+2kx^-3??

Answer 7

yup, now set that equal to zero and solve

Answer 8

...and plug in x=-1

Answer 9

because that's where the inflection point is...

Answer 10

then k=2?

Answer 11

yes

Answer 12

oh ok thanks so much everyone!! :)

Answer 13

welcome

Answer 14

especcially TuringTest :))