Math Problem Statement

In 2040, people all over the world were excited to discover Planet Z populated by friendly aliens. Scientists were working hard to make it technically possible to meet the new distant and long-awaited neighbors. This was difficult as many laws of nature on the planet appeared to be… “shifted“ compared to our blue planet. Additionally, most of the software/online problem solvers couldn’t help in preparations since they are tuned to our home planet environment. Even worse, people of 2040s rely on the computers completely and can do almost nothing “by hand” but now you're on board the spaceship #159881477, and the captain is asking to solve "ZP" (Z Planet) problem (you know what it means when captain is "asking"... that's an order):

Here Is The Story that happened to you earlier...

but now you're on board the spaceship #955032212, and the captain is asking to solve tricky "ZP" (Z Planet) problem (you know what it means when captain is "asking"... that's an order):

(!!! Do Not use decimals/calculator. Present fractions in an exact format, for example, 6110761107 , 2294222942)

Now, find the slope of the tangent line to the curve

x2−3xy+y3=49x2-3xy+y3=49

at the point (−2,3)(-2,3).

  

!!! The challenge is that the easiest differentiation rule on Earth, ddxxn=nxn−1ddxxn=nxn-1 , on Z planet is "twisted" as the following:

 ddxxn=n2xn−1ddxxn=n2xn-1  (ddxconst=0ddxconst=0 , and the other rules have not been changed).

Solution

Problem Restated:

You need to find the slope of the tangent line to the curve x23xy+y3=49x^2 - 3xy + y^3 = 49 at the point (2,3)(-2, 3). However, you are on Planet Z, where the power rule for differentiation is modified as:

ddxxn=n2xn1.\frac{d}{dx} \, x^n = n^2 \, x^{n-1}.

This twist will affect the derivative calculations involving terms like x2x^2, so let's carefully proceed step-by-step.


1. Use Implicit Differentiation

The curve is:

x23xy+y3=49.x^2 - 3xy + y^3 = 49.

Since yy is a function of xx (i.e., y=y(x)y = y(x)), we need to differentiate both sides with respect to xx, applying implicit differentiation.


2. Differentiate Each Term

Using the Planet Z power rule, let’s differentiate term by term.

(a) Differentiate x2x^2

ddx(x2)=22x21=4x.\frac{d}{dx} \, (x^2) = 2^2 \, x^{2-1} = 4x.

(b) Differentiate 3xy-3xy

We need to apply the product rule here:
ddx(3xy)=3(ddx(x)y+xdydx).\frac{d}{dx} \, (-3xy) = -3 \left( \frac{d}{dx}(x) \cdot y + x \cdot \frac{dy}{dx} \right).

  • ddx(x)=1\frac{d}{dx}(x) = 1, so the first part becomes 3y=3y-3 \cdot y = -3y.
  • The second part is 3xdydx=3xy-3x \cdot \frac{dy}{dx} = -3x \cdot y', where y=dydxy' = \frac{dy}{dx}.

Thus, the derivative of 3xy-3xy is: 3y3xy.-3y - 3x \cdot y'.

(c) Differentiate y3y^3

Using the chain rule and treating yy as a function of xx: ddx(y3)=32y31y=9y2y.\frac{d}{dx}(y^3) = 3^2 \, y^{3-1} \cdot y' = 9y^2 \cdot y'.

(d) Differentiate the constant 4949

Since the derivative of a constant is 00, we get: ddx(49)=0.\frac{d}{dx}(49) = 0.


3. Combine All Terms

Now, put everything together:

4x3y3xy+9y2y=0.4x - 3y - 3x \cdot y' + 9y^2 \cdot y' = 0.

Rearrange terms so that all the yy' terms are on the right:

3xy+9y2y=3y4x.-3x \cdot y' + 9y^2 \cdot y' = 3y - 4x.

Factor out yy' on the left:

y(9y23x)=3y4x.y' \left( 9y^2 - 3x \right) = 3y - 4x.

Solve for yy':

y=3y4x9y23x.y' = \frac{3y - 4x}{9y^2 - 3x}.


4. Evaluate the Derivative at the Point (2,3)(-2, 3)

We need to find the slope of the tangent line at the point (2,3)(-2, 3). Substitute x=2x = -2 and y=3y = 3 into the derivative:

y=3(3)4(2)9(3)23(2).y' = \frac{3(3) - 4(-2)}{9(3)^2 - 3(-2)}.

Simplify the numerator:

3(3)4(2)=9+8=17.3(3) - 4(-2) = 9 + 8 = 17.

Simplify the denominator:

9(9)3(2)=81+6=87.9(9) - 3(-2) = 81 + 6 = 87.

Thus, the slope of the tangent line is:

y=1787.y' = \frac{17}{87}.


5. Final Answer

The slope of the tangent line to the curve at the point (2,3)(-2, 3) is:

1787.\boxed{\frac{17}{87}}.


Do You Have Any Questions?


5 Follow-Up Questions:

  1. What is implicit differentiation, and why is it used here?
  2. How does the modified power rule change standard calculus operations?
  3. Can you derive the product rule on Planet Z using the twisted power rule?
  4. How would the slope change if the differentiation rules for yy were also modified?
  5. What is the geometric significance of the slope of the tangent line?

One Tip:

When using implicit differentiation, always remember to treat yy as a function of xx, and apply the product or chain rule where necessary!

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Tangent Line
Modified Power Rule

Formulas

d/dx(x^n) = n²x^(n−1) (Planet Z Power Rule)
Implicit Differentiation Formula
Product Rule: d/dx(uv) = u'(v) + u(v')
Slope of Tangent Line Formula: dy/dx

Theorems

Product Rule
Chain Rule

Suitable Grade Level

Grades 11-12