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Mathematics 15 Online
Ballery1:

Math help plz

Ballery1:

Find the equation of the tangent line to the curve in the day-plane given by \[x^3+y^3 = 9 \]

Ballery1:

Do I need to use the implicitly differentiation to find the derivative first, then plugin the x-value ...as given in the question...to find the instantaneous rate of change at that point ...once I have the slope, points.. I can use the y = my+b equation to write the equation of the tangent line correct?

Ballery1:

@DuarteME

Ballery1:

I mean plugin both x and y values in to the implicitly differentiation and get my instantaneous rate of change at that particular point...

Ballery1:

I got dry/do = -x^/y^2 as an answer to that equation... so far.. now i’m Going to plugin the points into the derivative

Ballery1:

Let me draw what I did..one second plz

Ballery1:

|dw:1569451796248:dw|/

DuarteME:

Well, in this case, we are dealing with cubics and they are invertible everywhere, so you can solve the equation for \(y\) and find \(\frac{\textrm{d}y}{\textrm{d}x}\). This might not be so easy in general. For instance, say you are dealing with a curve defined by \(y\textrm{e}^{xy} = 3x\). Implicit differentiation is also okay and you'll probably get the answer faster. Your work seems fine so far. (:

Ballery1:

Thanks master. Really appreciated your feedback. God bless you!! <3 :) I will post the final answer in a bit. :)

Ballery1:

|dw:1569453133881:dw|

DuarteME:

Nice job! You seem to have lost the \(x\) just before the arrow, but other than that it looks great!

Ballery1:

Oh yeah...sorry lol...thanks master! *BOWS*.

Ballery1:

Now i’m Going to start the applications of derivatives ...where the graph is increasing and decreasing and stuff... in the next chapter.. :)

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