Home
Class 14
MATHS
If x+ (1)/(x)=1, find x^(10) + (1)/(x...

If `x+ (1)/(x)=1`, find
`x^(10) + (1)/(x^(10))=`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the equation \( x + \frac{1}{x} = 1 \) and find \( x^{10} + \frac{1}{x^{10}} \), we can follow these steps: ### Step 1: Start with the given equation We have: \[ x + \frac{1}{x} = 1 \] ### Step 2: Cube both sides To find \( x^3 + \frac{1}{x^3} \), we can use the identity: \[ \left( a + b \right)^3 = a^3 + b^3 + 3ab(a + b) \] Letting \( a = x \) and \( b = \frac{1}{x} \), we cube both sides: \[ \left( x + \frac{1}{x} \right)^3 = 1^3 \] This gives us: \[ x^3 + \frac{1}{x^3} + 3 \cdot x \cdot \frac{1}{x} \cdot (x + \frac{1}{x}) = 1 \] Since \( x \cdot \frac{1}{x} = 1 \), we simplify: \[ x^3 + \frac{1}{x^3} + 3 \cdot 1 \cdot 1 = 1 \] Thus: \[ x^3 + \frac{1}{x^3} + 3 = 1 \] ### Step 3: Solve for \( x^3 + \frac{1}{x^3} \) Rearranging gives: \[ x^3 + \frac{1}{x^3} = 1 - 3 = -2 \] ### Step 4: Find \( x^6 + \frac{1}{x^6} \) Next, we use the identity again: \[ \left( x^3 + \frac{1}{x^3} \right)^2 = x^6 + \frac{1}{x^6} + 2 \] Substituting \( x^3 + \frac{1}{x^3} = -2 \): \[ (-2)^2 = x^6 + \frac{1}{x^6} + 2 \] This simplifies to: \[ 4 = x^6 + \frac{1}{x^6} + 2 \] Thus: \[ x^6 + \frac{1}{x^6} = 4 - 2 = 2 \] ### Step 5: Find \( x^9 + \frac{1}{x^9} \) Now we find \( x^9 + \frac{1}{x^9} \) using: \[ x^9 + \frac{1}{x^9} = (x^6 + \frac{1}{x^6})(x^3 + \frac{1}{x^3}) - (x^3 + \frac{1}{x^3}) \] Substituting the known values: \[ x^9 + \frac{1}{x^9} = (2)(-2) - (-2) \] This simplifies to: \[ x^9 + \frac{1}{x^9} = -4 + 2 = -2 \] ### Step 6: Find \( x^{10} + \frac{1}{x^{10}} \) Finally, we find \( x^{10} + \frac{1}{x^{10}} \) using: \[ x^{10} + \frac{1}{x^{10}} = (x^9 + \frac{1}{x^9})(x + \frac{1}{x}) - (x^8 + \frac{1}{x^8}) \] We already have \( x + \frac{1}{x} = 1 \) and need \( x^8 + \frac{1}{x^8} \): \[ x^8 + \frac{1}{x^8} = (x^6 + \frac{1}{x^6})(x^2 + \frac{1}{x^2}) - (x^4 + \frac{1}{x^4}) \] We need \( x^2 + \frac{1}{x^2} \): \[ \left( x + \frac{1}{x} \right)^2 = x^2 + \frac{1}{x^2} + 2 \] So: \[ 1^2 = x^2 + \frac{1}{x^2} + 2 \implies 1 = x^2 + \frac{1}{x^2} + 2 \implies x^2 + \frac{1}{x^2} = -1 \] Now substituting back: \[ x^4 + \frac{1}{x^4} = (x^2 + \frac{1}{x^2})^2 - 2 = (-1)^2 - 2 = 1 - 2 = -1 \] Now substituting into \( x^8 + \frac{1}{x^8} \): \[ x^8 + \frac{1}{x^8} = (2)(-1) - (-1) = -2 + 1 = -1 \] Finally substituting into \( x^{10} + \frac{1}{x^{10}} \): \[ x^{10} + \frac{1}{x^{10}} = (-2)(1) - (-1) = -2 + 1 = -1 \] ### Final Answer Thus, the value of \( x^{10} + \frac{1}{x^{10}} \) is: \[ \boxed{-1} \]
Promotional Banner

Topper's Solved these Questions

  • AVERAGE

    ADVANCED MATHS BY ABHINAY MATHS ENGLISH|Exercise QUESTIONS|115 Videos

Similar Questions

Explore conceptually related problems

If the average of x and 1/x be 1 , then the value of x^(10) +(1)/(x^(10)) is

(i) If (1)/(9!)+(1)/(10!)=(n)/(11!) , find n. (ii) If (1)/(8!)+(1)/(9!)=(x)/(10!) , find x.

lim_ (x rarr oo) ((x + 2) ^ (10) + (x + 4) ^ (10) ++ (x + 20) ^ (10)) / (x ^ (10) +1) =

Find the coefficient of x^(8) in the expansion of (x^(2)-(1)/(x))^(10)

Lim_(x rarr1)(x^(15)-1)/(x^(10)-1)

Coefficient of x^(8) in (1+x)^(10) + x(1+x)^(9) + x^(2)(1+x)^(8) + ………….x^(9)(1+x) + x^(10) is