If [tex]x=\left(\frac{5-\sqrt{2}}{2}\right)[/tex], find [tex]\left(x^3+\frac{1}{x^3}\right)-5\left(x^3+\frac{1}{x^2}\right)+\left(x+\frac{1}{x}\right)[/tex].



Answer :

Given that [tex]\( x = \left( \frac{5 - \sqrt{2}}{2} \right) \)[/tex], we need to find the value of the expression:

[tex]\[ \left(x^3 + \frac{1}{x^3}\right) - 5\left(x^2 + \frac{1}{x^2}\right) + \left(x + \frac{1}{x}\right) \][/tex]

Let's break it down step-by-step:

### Step 1: Calculate [tex]\( x^3 \)[/tex] and [tex]\( \frac{1}{x^3} \)[/tex]

First, evaluate [tex]\( x^3 \)[/tex]:

[tex]\[ x^3 = 5.76319446215896 \][/tex]

Then, evaluate [tex]\( \frac{1}{x^3} \)[/tex]:

[tex]\[ \frac{1}{x^3} = 0.17351488077766306 \][/tex]

### Step 2: Calculate [tex]\( x^2 \)[/tex] and [tex]\( \frac{1}{x^2} \)[/tex]

Next, evaluate [tex]\( x^2 \)[/tex]:

[tex]\[ x^2 = 3.2144660940672627 \][/tex]

Then, evaluate [tex]\( \frac{1}{x^2} \)[/tex]:

[tex]\[ \frac{1}{x^2} = 0.31109365310949677 \][/tex]

### Step 3: Calculate [tex]\( x \)[/tex] and [tex]\( \frac{1}{x} \)[/tex]

Now, evaluate [tex]\( x \)[/tex]:

[tex]\[ x = 1.7928932188134525 \][/tex]

Then, evaluate [tex]\( \frac{1}{x} \)[/tex]:

[tex]\[ \frac{1}{x} = 0.5577577010759213 \][/tex]

### Step 4: Combine the results

Now, plug these values into the original expression:

[tex]\[ \left(x^3 + \frac{1}{x^3}\right) - 5\left(x^2 + \frac{1}{x^2}\right) + \left(x + \frac{1}{x}\right) \][/tex]

Start with the cubic terms:

[tex]\[ x^3 + \frac{1}{x^3} = 5.76319446215896 + 0.17351488077766306 = 5.936709342936623 \][/tex]

Next, the quadratic terms multiplied by 5:

[tex]\[ 5 \left( x^2 + \frac{1}{x^2} \right) = 5 \left( 3.2144660940672627 + 0.31109365310949677 \right) = 5 \times 3.5255597471767595 = 17.6277987358837975 \][/tex]

Then, the linear terms:

[tex]\[ x + \frac{1}{x} = 1.7928932188134525 + 0.5577577010759213 = 2.3506509198893738 \][/tex]

Finally, combine all the terms to find the result:

[tex]\[ \left( 5.936709342936623 \right) - \left( 17.6277987358837975 \right) + \left( 2.3506509198893738 \right) = -9.3404384730578 \][/tex]

Thus, the value of the given expression is:

[tex]\[ \boxed{-9.3404384730578} \][/tex]