Math Problem Statement

Find the maximum and minimun value

Find the maximum and minimum value of the polynomial function f(x) = 5x^6 - 18x^5 + 15x^4 - 10.

Solution

The given expression is:

f(x)=5x618x5+15x410f(x) = 5x^6 - 18x^5 + 15x^4 - 10

To find the maximum and minimum values of f(x)f(x), follow these steps:

Step 1: Compute the first derivative

The first derivative is:

f(x)=30x590x4+60x3f'(x) = 30x^5 - 90x^4 + 60x^3

Step 2: Factorize f(x)f'(x)

Factorize the derivative:

f(x)=30x3(x23x+2)f'(x) = 30x^3(x^2 - 3x + 2)

Factorize x23x+2x^2 - 3x + 2:

f(x)=30x3(x1)(x2)f'(x) = 30x^3(x - 1)(x - 2)

Step 3: Critical points

Set f(x)=0f'(x) = 0:

30x3(x1)(x2)=030x^3(x - 1)(x - 2) = 0

The critical points are:

x=0,x=1,x=2x = 0, \, x = 1, \, x = 2

Step 4: Second derivative test

The second derivative is:

f(x)=150x4360x3+180x2f''(x) = 150x^4 - 360x^3 + 180x^2

Evaluate f(x)f''(x) at each critical point:

  1. At x=0x = 0: f(0)=150(0)4360(0)3+180(0)2=0f''(0) = 150(0)^4 - 360(0)^3 + 180(0)^2 = 0 The test is inconclusive for x=0x = 0.

  2. At x=1x = 1: f(1)=150(1)4360(1)3+180(1)2=150360+180=30f''(1) = 150(1)^4 - 360(1)^3 + 180(1)^2 = 150 - 360 + 180 = -30 Since f(1)<0f''(1) < 0, f(x)f(x) has a local maximum at x=1x = 1.

  3. At x=2x = 2: f(2)=150(2)4360(2)3+180(2)2=150(16)360(8)+180(4)f''(2) = 150(2)^4 - 360(2)^3 + 180(2)^2 = 150(16) - 360(8) + 180(4) Simplify: f(2)=24002880+720=240f''(2) = 2400 - 2880 + 720 = 240 Since f(2)>0f''(2) > 0, f(x)f(x) has a local minimum at x=2x = 2.

Step 5: Evaluate f(x)f(x) at critical points

Compute f(x)f(x) at x=0,x=1,x = 0, x = 1, and x=2x = 2:

  1. At x=0x = 0: f(0)=5(0)618(0)5+15(0)410=10f(0) = 5(0)^6 - 18(0)^5 + 15(0)^4 - 10 = -10

  2. At x=1x = 1: f(1)=5(1)618(1)5+15(1)410=518+1510=8f(1) = 5(1)^6 - 18(1)^5 + 15(1)^4 - 10 = 5 - 18 + 15 - 10 = -8

  3. At x=2x = 2: f(2)=5(2)618(2)5+15(2)410f(2) = 5(2)^6 - 18(2)^5 + 15(2)^4 - 10 Simplify: f(2)=5(64)18(32)+15(16)10=320576+24010=26f(2) = 5(64) - 18(32) + 15(16) - 10 = 320 - 576 + 240 - 10 = -26

Results

  • Local maximum: f(1)=8f(1) = -8 at x=1x = 1.
  • Local minimum: f(2)=26f(2) = -26 at x=2x = 2.
  • At x=0x = 0, f(0)=10f(0) = -10 (neither max nor min).

Would you like detailed graphs or further analysis?


Related Questions:

  1. How can the global maximum and minimum of a polynomial be confirmed?
  2. What is the significance of the second derivative test in optimization?
  3. How does factoring simplify finding critical points?
  4. Could the endpoints of a domain affect the max/min values?
  5. How is f(x)=0f'(x) = 0 connected to real-world applications?

Tip: Always check endpoints if the domain is restricted, as they may yield absolute extrema.

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Math Problem Analysis

Mathematical Concepts

Calculus
Polynomials
Optimization
Derivatives

Formulas

First derivative f'(x) to find critical points
Second derivative f''(x) for concavity and the second derivative test

Theorems

Critical points theorem
Second derivative test for extrema

Suitable Grade Level

Grades 11-12 and College