Implicit Differentiation; Tangent Line

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Homework Help Overview

The discussion revolves around finding the equation of a tangent line to the curve defined by the equation x^(1/3) + y^(1/3) = 4 at the point (-3√3, 1). Participants are working through the process of implicit differentiation to determine the slope of the tangent line.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss taking the derivative of the equation and express uncertainty about the correctness of their results. There are questions regarding potential typos in the original equation and how that affects the differentiation process. Some participants also explore different forms of the expression for the slope.

Discussion Status

There is an ongoing exploration of the derivative and its implications for finding the slope of the tangent line. Participants have provided some guidance and clarification regarding the original equation, but there is no explicit consensus on the correct slope yet.

Contextual Notes

There is mention of a possible typo in the original equation, which has led to confusion in the differentiation process. The specific values being plugged into the derivative have resulted in complications, contributing to the uncertainty in the discussion.

b521
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Homework Statement


Find the equation of a tangent line at the curve at point (-3√3, 1)

x^(1/3) + y^(1/3) = 4

Homework Equations


Point-slope:
y-1=m(x-1)

The Attempt at a Solution



I took the derivative of that equation and resulted in
-y^(2/3)/x^(2/3)

When I tried plugging in x and y to get slope, the equation got very messy and I couldn't get a number out of it. Can anyone help me out?
 
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b521 said:

Homework Statement


Find the equation of a tangent line at the curve at point (-3√3, 1)

x^(1/3) = y^(1/3) = 4
Looks like there is a typo here.
b521 said:

Homework Equations


Point-slope:
y-1=m(x-1)
This would be the line with slope m, that passes through (1, 1).
b521 said:

The Attempt at a Solution



I took the derivative of that equation and resulted in
y^(2/3)/x^(2/3)
It's hard to tell whether this is correct, since the original equation likely has a typo. If you typed '=' in place of '+', then you have a sign error in your derivative. Also, it would be helpful to have an equation for your derivative; e.g., y' = y^(2/3)/x^(2/3).
b521 said:
When I tried plugging in x and y to get slope, the equation got very messy and I couldn't get a number out of it. Can anyone help me out?
 
Here's all of my work:

(1/3)x^(-2/3) + 1/3y^(-2/3)(dy/dx) = 0

(dy/dx)1/3y^(2/3) = -1/3x^(2/3)
dy/dx = -3y^(2/3)/3x^(2/3)
dy/dx = -y^(2/3)/x^(2/3)

I hope that helps find my problem. This is where I tried plugging in the x value and everything got complicated.

1/(-3√3)^(2/3)
 
What is the original equation? I can't tell if your work is correct without knowing the original equation.
 
(-3√3)^(2/3) can also be written as ((-3√3)^2)^(1/3)
 
Mark44 said:
What is the original equation? I can't tell if your work is correct without knowing the original equation.

x^(1/3) + y^(1/3) = 4

This is the original equation. Sorry about the typo before.
 
That's what I thought, but I wanted to make sure. You should have enough information to complete the problem now.
 
Mark44 said:
(-3√3)^(2/3) can also be written as ((-3√3)^2)^(1/3)

Just to make sure, the slope is 1/3?
 

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