5th degree polynomial question4





In this page 5th degree polynomial question4 we are going to see how to solve the polynomial which is having degree 5.

Question 4 :

Solve  x⁵ - 5 x³ + 5 x² - 1

Solution :

The degree of this equation is 5. Therefore we can say there will be 5 roots for this equation.

This is a reciprocal equation of odd degree with unlike terms. So 1 is one of the root of this equation. 

The other roots are given by

x⁴ + x³ - 4 x² +  x + 1= 0

Dividing the entire equation by x²

 x⁴/x² + x³/x² - 4 x²/x² + x/x² + 1/x² = 0

 x² + x - 4  + 1/x + 1/x² = 0

 (x² + 1/x²)  - 4  + (1/x) + x = 0

(x² + 1/x²) + (x + 1/x) - 4 = 0 ------ (1)

Let x + 1/x = y

To find the value of x² + 1/x² from this we have to take squares on both sides

(x + 1/x)² = y²

x² + 1/x² + 2 x (1/x) = y²

x² + 1/x² + 2 = y²

x² + 1/x² = y² - 2

So we have to plug y² - 2 instead of x² + 1/x²

Let us plug this value in the first equation

(y² - 2) + y - 4 = 0

y² - 2 + y - 4 = 0

y² + y - 6 = 0

y² + 3 y - 2 y - 6 = 0

y (y + 3) - 2 (y + 3) = 0

(y + 3) (y - 2) = 0

y + 3 = 0

    y = -3

    y = -3

y - 2 = 0

     y = 2

     y = 2

x + 1/x = y

(x² + 1)/x = -3

(x² + 1) = -3 x

x² + 1 + 3x = 0

x² + 3x + 1  = 0  5th degree polynomial question4

   x = (-3 ± √5)/2

 x + 1/x = y

(x² + 1)/x = 2

(x² + 1) = 2x

x² - 2 x + 1 = 0

x² - 1 x - 1 x + 1 = 0

x (x - 1) - 1(x - 1) = 0

(x - 1) (x - 1) = 0

(x - 1) = 0          (x - 1) = 0

        x = 1                x = 1

       x = 1

Therefore the 5 roots are x = 1,1,1,(-3 ± √5)/2
5th degree polynomial question1

This is the example problem in the topic solving polynomial of degree5. You can try the following sample test to understand this topic much better.


Questions



Solution


Question 1 :

Solve 6 x⁵ - x⁴ - 43 x³ + 43 x² + x - 6


Solution

Question 2 :

Solve 8 x⁵ - 22 x⁴ - 55 x³ + 55 x² + 22 x - 8


Solution

Question 3 :

Solve  x⁵ - 5 x⁴ + 9 x³ - 9 x² + 5 x - 1


Solution

Question 5 :

Solve  6 x⁵ + 11 x⁴ - 33 x³ - 33 x² + 11 x + 6


Solution






5th Degree Polynomial Question4 to Algebra