Question

mathcalculus
HELP: Determine the values of where the tangent line is horizontal for the function:

Answer 1

i know i have to find the derivative and set it to zero but it's not coming out to be correct. can anyone help me

Answer 2

so i did 3x^2-6x-4=0

Answer 3

i tried to use the quadratic formula and got sqrt(21)+3/3

Answer 4

+ or - sqrt(21)+3/3

Answer 5

also aka 2.52753...

Answer 6

derivative seems correct

Answer 7

to find what x = to... ?

Answer 8

i used quadratic formula

Answer 9

@dumbcow dont i have to do that to find x??

Answer 10

im getting it wrong,

Answer 11

yes everything looks correct to me...do they want exact or decimal answer?

Answer 12

http://www.wolframalpha.com/input/?i=3x%5E2-6x-4%3D0

Answer 13

can i use quadratic formula for ths one?

Answer 14

@dumbcow

Answer 15

??

Answer 16

????????????????????????

Answer 17

yes of course you use quadratic formula...thats how you got your answer that i said looked correct

Answer 18

im not getting that using quadratic formula

Answer 19

im getting something totally different and wrong

Answer 20

\[x = \frac{3 \pm \sqrt{21}}{3}\]

Answer 21

yes! but from 6+2*sqrt(21)/6?

Answer 22

shouldnt it be 1+ or - sqrt 21/3

Answer 23

same thing, just a matter of splitting up fraction or keeping it as single fraction

Answer 24

no it's not because the answer is 1+ sqrt (7/3) gives me 2.52753 and 1+sqrt 21/3 gives me 1.86086!

Answer 25

@dumbcow

Answer 26

hmm
\[\frac{\sqrt{7}}{\sqrt{3}} = \frac{\sqrt{21}}{3} \]

Answer 27

hmmm?

Answer 28

@dumbcow

Answer 29

try it on a calculator.

Answer 30

http://www.wolframalpha.com/input/?i=1%2Bsqrt%287%2F3%29+%2C+1%2Bsqrt%2821%29%2F3

Answer 31

oh you added the "1" before dividing by "3"

Answer 32

okay from my answer.... not the internet.. 6+2 sort(21)/3.... where do i go from there?

Answer 33

well it should be a 6 on bottom

Answer 34

no i didn't add anything.

Answer 35

okay sure a 6. i thought it could be a 3 to narrow it down

Answer 36

so 6+or-2sqrt(21)/6

Answer 37

i dont see the problem, you posted answer in beginning...

" i tried to use the quadratic formula and got sqrt(21)+3/3 "

Answer 38

so it is a 3 in the denominator!

Answer 39

\[\frac{6 \pm 2\sqrt{21}}{6} = \frac{2(3 \pm \sqrt{21})}{6} = \frac{3 \pm \sqrt{21}}{3}\]