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Mathematics 23 Online
OpenStudy (anonymous):

need help

OpenStudy (anonymous):

OpenStudy (amistre64):

\[f(x) = \frac{(2x+3)}{(3x-2)}\] we need to find its derivative

OpenStudy (amistre64):

we also need to determine the value of f(1)

OpenStudy (anonymous):

yes, but how would take the derivative with that function?

OpenStudy (amistre64):

by using what is so adequately refered to as: the quotient rule

OpenStudy (amistre64):

Do you know the derivative rules yet?

OpenStudy (amistre64):

we could also get by with bringing the bottom to the top and placing a negative exponent on it and derive it with the product rule

OpenStudy (anonymous):

Well we haven't cover the quotient rule yet, but if you could use it to show me I would appreciate because I believe my professor was going to cover, but ran out of time

OpenStudy (amistre64):

\[\frac{top}{bottom}\] \[Dx\ (\frac{t}{b}) = \frac{bt'-b't}{b^2}\]

OpenStudy (amistre64):

does that make sense as written?

OpenStudy (anonymous):

yes

OpenStudy (amistre64):

good, find the derivates of the top and the bottom, then plug them into the right spots in the formula

OpenStudy (anonymous):

OpenStudy (amistre64):

keep attantion to your signs; youve got some mismatched

OpenStudy (amistre64):

its good form except for you should have (3x-2), not (3x+2).

OpenStudy (amistre64):

unless of course i mistyped the original :)

OpenStudy (amistre64):

when you have it all squared away, find f'(1) by using x=1 in the derivative to find the value of the slope of the tangent line at f(1)

OpenStudy (anonymous):

I get f(1)=-13

OpenStudy (anonymous):

what do I do next?

OpenStudy (amistre64):

i got -14 .... you sure?

OpenStudy (amistre64):

lol ... its -13

OpenStudy (amistre64):

that is the slope of the tangent line; use it in the slope point form of an equation

OpenStudy (amistre64):

y-f(1) = f'(1)(x-1)

OpenStudy (anonymous):

I got y=-13x+18

OpenStudy (anonymous):

did you get the same?

OpenStudy (amistre64):

y-f(1) = f'(1)(x-1) y-5 = -13x +13 .. yes

OpenStudy (anonymous):

yes

OpenStudy (anonymous):

whats next?

OpenStudy (amistre64):

thats it, you found the equation of the tangent line at 1,f(1)

OpenStudy (amistre64):

just match it to one of the formats they present

OpenStudy (amistre64):

id go with C myself

OpenStudy (anonymous):

But c has a positive 13 in front of the x and our answer has -13 front of the x

OpenStudy (amistre64):

y = -13x + 18 +13x +13x ----------------- 13x+y = 18

OpenStudy (amistre64):

you have to move stuff around to match what they present

OpenStudy (anonymous):

Thank you!

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