Multi-variable Polynomial Optimization Using Factor & Remainder Theorems

00:00 10 marks

  • Exam Style - Paper 3
  • HL
  • Tier 4
  • Remainder Theorem
  • Factor Theorem
  • Optimization
  • Critical points
  • Sum and Product of Roots
  • Polynomial Modeling

A company models its profit using a polynomial function \(f(x, y)\), where \(x\) represents the number of units produced and \(y\) represents the number of units sold. The goal is to maximize this profit.

(a) Propose a feasible polynomial model for the profit function \(f(x, y)\) that incorporates production costs that increase with production quantity and revenue that depends on both units produced and sold. Include fixed costs in your model.

(b) Factorize the terms involving \(x\) in your proposed polynomial model using factorization techniques to identify potential critical values for production level \(x\).

(c) Interpret the significance of the critical values found in part (b) in the context of the company’s profit optimization. Explain what these values suggest about the company’s production strategy.

Part a

5 minutes 3 marks

Question

Propose a polynomial model for the company’s profit \(f(x, y)\) as a function of units produced \(x\) and units sold \(y\). Your model should incorporate:
(i) Revenue that increases with both \(x\) and \(y\).
(ii) Production costs that increase with \(x\), including a component that increases at an increasing rate.
(iii) Fixed operating costs.



Hint Hint

Hint

Consider terms like \(xy\) for revenue, \(x^2\) for increasing production costs, \(ax\) for variable costs, and \(b\) for fixed costs. Combine these into a profit function.

  • Answer Answer

Complete Answer

A feasible polynomial model is \(f(x, y) = xy – x^2 – ax – b\), where:
\(xy\) represents revenue, increasing with both production and sales.
\(-x^2\) represents production costs increasing at an increasing rate with production.
\(-ax\) represents variable production costs.
\(-b\) represents fixed operating costs.

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Part b

5 minutes 4 marks

Question

Using the polynomial model \(f(x, y) = y(x^2 – 5x + 6) + ax + b\), factorize the quadratic expression in \(x\) to identify potential critical values for \(x\). Show your factorization steps.



Hint Hint

Hint

Focus on factorizing the quadratic expression \(x^2 – 5x + 6\). Recall factorization techniques for quadratic equations.

  • Answer Answer

Complete Answer

To factorize \(f(x, y) = y(x^2 – 5x + 6) + ax + b\), we focus on the quadratic part \(x^2 – 5x + 6\).
\(x^2 – 5x + 6 = (x-2)(x-3)\)
Thus, the factorized form is \(f(x, y) = y(x-2)(x-3) + ax + b\). The factors \((x-2)\) and \((x-3)\) suggest potential critical values at \(x=2\) and \(x=3\).

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Part c

5 minutes 3 marks

Question

Interpret the critical values \(x=2\) and \(x=3\) in the context of the company’s profit optimization strategy. What do these values of production level \(x\) suggest about maximizing profit? What further steps might the company take to confirm optimal production levels?



Hint Hint

Hint

Consider what critical points mean for the rate of change of profit. Think about local maxima, minima, and the need for further analysis to confirm optimality.

  • Answer Answer

Complete Answer

The critical values \(x=2\) and \(x=3\) suggest production levels where the profit function \(f(x, y)\) may have a local maximum or minimum with respect to \(x\). In terms of profit optimization, these values indicate production quantities that could potentially lead to the highest or lowest profit. To confirm whether these are optimal production levels, the company should perform further analysis using calculus, such as finding partial derivatives of \(f(x, y)\) with respect to \(x\) and \(y\) and analyzing the second derivative to determine the nature of these critical points (maxima, minima, or saddle points).

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