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Mathematics 18 Online
OpenStudy (babynini):

Graphs and derivatives!

OpenStudy (babynini):

help!

OpenStudy (babynini):

@dan815

jimthompson5910 (jim_thompson5910):

are you able to determine what `P ' (x)` is?

OpenStudy (babynini):

Em, you mean with the product rule?

jimthompson5910 (jim_thompson5910):

yes

OpenStudy (babynini):

p'(x) = f'(x)g(x)+f(x)g'(x)

jimthompson5910 (jim_thompson5910):

yep

jimthompson5910 (jim_thompson5910):

now replace every x with 2

jimthompson5910 (jim_thompson5910):

P ' (x) = F '(x)*G(x) + F(x)*G ' (x) P ' (2) = F '(2)*G(2) + F(2)*G ' (2)

jimthompson5910 (jim_thompson5910):

F(2) and G(2) are simply the y coordinates on F(x) and G(x) respectively when x = 2

jimthompson5910 (jim_thompson5910):

F ' (2) is the slope of the tangent line on F(x) when x = 2 G ' (2) is the slope of the tangent line on G(x) when x = 2

OpenStudy (babynini):

Wait wait, so now we have p'(2)=f'(2)g(2)+f(2)g'(2)

OpenStudy (babynini):

f(2) = 3 g(2)=2

jimthompson5910 (jim_thompson5910):

`f(2) = 3` `g(2)=2` yes on both

OpenStudy (babynini):

f'(2) = 0 g'(2) = ..?

OpenStudy (babynini):

ooh oh g'(2) = 1/2

jimthompson5910 (jim_thompson5910):

yes on those two as well

OpenStudy (babynini):

p'(2) = 3/2 ?

jimthompson5910 (jim_thompson5910):

yep

OpenStudy (babynini):

q'(x) = 3/8?

OpenStudy (babynini):

hrrm no I did it wrong.

OpenStudy (babynini):

Where did I do it wrong? q'(x) = [g(x)f'(x) - f(x)g'(x)]/g(x)^2

OpenStudy (babynini):

q'(x) = [2(0)-3(1/2)]/4

jimthompson5910 (jim_thompson5910):

we want Q ' (7), not Q ' (2)

OpenStudy (babynini):

oou...

OpenStudy (babynini):

q'(7) = 43/12?

jimthompson5910 (jim_thompson5910):

yep

OpenStudy (babynini):

Yay!! thank you :)

jimthompson5910 (jim_thompson5910):

you're welcome

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