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Mathematics 10 Online
OpenStudy (anonymous):

please explain

OpenStudy (loser66):

what is the point?

OpenStudy (jhannybean):

@Loser66 knows this really well :P

OpenStudy (loser66):

Your question: "Does this tangent line lie above or below the graph at this point" My question: what is the point?

OpenStudy (loser66):

is it (3,4)??

OpenStudy (loser66):

I admire mondona, he never gives up. hehehe... He makes this question more than 3times. :)

OpenStudy (jhannybean):

lol?? Perseverance!

ganeshie8 (ganeshie8):

find the second derivative

ganeshie8 (ganeshie8):

\[g'(x) = \dfrac{x^2-16}{x-2}\] \[g''(x) = ?\]

OpenStudy (loser66):

knock knock @mondona

ganeshie8 (ganeshie8):

how ? you need to use quotient rule to find the derivative

ganeshie8 (ganeshie8):

doesnt look correct, try again and show all steps so that i can pinpoint the mistake

ganeshie8 (ganeshie8):

right, next step

OpenStudy (skullpatrol):

Do you know why you are calculating the second derivative?

ganeshie8 (ganeshie8):

\[g'(x) = \dfrac{x^2-16}{x-2}\] \[g''(x) = \dfrac{\frac{d}{dx}(x^2-16) (x-2) - \frac{d}{dx}(x-2)(x^2-16)}{(x-2)^2}\] \[g''(x) = \dfrac{(2x) (x-2) - (1)(x^2-16)}{(x-2)^2}\] yes ?

ganeshie8 (ganeshie8):

distribute and simplify the numerator

ganeshie8 (ganeshie8):

\[g''(x) = \dfrac{2x^2-4x - x^2+16}{(x-2)^2}\]

ganeshie8 (ganeshie8):

\[g''(x) = \dfrac{x^2-4x+16}{(x-2)^2}\]

ganeshie8 (ganeshie8):

still yes ?

ganeshie8 (ganeshie8):

good, find g''(3)

ganeshie8 (ganeshie8):

plugin x=3 above

ganeshie8 (ganeshie8):

which is positive

ganeshie8 (ganeshie8):

g''(3) > 0 so can we say the graph of g(x) is concave up (valley) at x=3 ?

ganeshie8 (ganeshie8):

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