5. If [tex]$x - \frac{1}{x} = 5[tex]$[/tex], find [tex]$[/tex]x^2 + \frac{1}{x^2}[tex]$[/tex] and [tex]$[/tex]x^4 + \frac{1}{x^4}$[/tex].



Answer :

Certainly! Here is a detailed, step-by-step solution to find \(x^2 + \frac{1}{x^2}\) and \(x^4 + \frac{1}{x^4}\) given that \(x - \frac{1}{x} = 5\).

### Step 1: Square the given equation

Given:
[tex]\[ x - \frac{1}{x} = 5 \][/tex]

Square both sides of the equation:
[tex]\[ \left( x - \frac{1}{x} \right)^2 = 5^2 \][/tex]

Expand the left-hand side:
[tex]\[ x^2 - 2 \cdot x \cdot \frac{1}{x} + \left( \frac{1}{x} \right)^2 = 25 \][/tex]

Simplify:
[tex]\[ x^2 - 2 + \frac{1}{x^2} = 25 \][/tex]

### Step 2: Isolate \(x^2 + \frac{1}{x^2}\)

Add 2 to both sides to isolate the term we need:
[tex]\[ x^2 + \frac{1}{x^2} = 25 + 2 \][/tex]
[tex]\[ x^2 + \frac{1}{x^2} = 27 \][/tex]

### Step 3: Square the result to find \(x^4 + \frac{1}{x^4}\)

Next, we need to find \( x^4 + \frac{1}{x^4} \).

Square the equation we found in Step 2:
[tex]\[ \left( x^2 + \frac{1}{x^2} \right)^2 = 27^2 \][/tex]

Expand the left-hand side:
[tex]\[ x^4 + 2 \cdot x^2 \cdot \frac{1}{x^2} + \frac{1}{x^4} = 729 \][/tex]

Simplify:
[tex]\[ x^4 + 2 + \frac{1}{x^4} = 729 \][/tex]

### Step 4: Isolate \(x^4 + \frac{1}{x^4}\)

Subtract 2 from both sides to isolate the term we need:
[tex]\[ x^4 + \frac{1}{x^4} = 729 - 2 \][/tex]
[tex]\[ x^4 + \frac{1}{x^4} = 727 \][/tex]

### Summary

- The value of \( x^2 + \frac{1}{x^2} \) is \(27\).
- The value of \( x^4 + \frac{1}{x^4} \) is \(727\).

So, we have:
[tex]\[ x^2 + \frac{1}{x^2} = 27 \][/tex]
[tex]\[ x^4 + \frac{1}{x^4} = 727 \][/tex]