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Let f : R to R be defined by f(x) = ax...

Let `f : R to R` be defined by
`f(x) = ax + b AA x in R`
Where `a,b in R` and `a ne 1`
If `(fofofofof)(x) `= `32x + 93`, then value of b is ………….

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The correct Answer is:
To solve the problem, we need to find the value of \( b \) given that \( f(x) = ax + b \) and \( (f \circ f \circ f \circ f \circ f)(x) = 32x + 93 \). ### Step-by-Step Solution: 1. **Understanding the Function**: We start with the function \( f(x) = ax + b \). 2. **Finding \( f(f(x)) \)**: We substitute \( f(x) \) into itself: \[ f(f(x)) = f(ax + b) = a(ax + b) + b = a^2x + ab + b \] This can be rewritten as: \[ f(f(x)) = a^2x + (ab + b) \] 3. **Finding \( f(f(f(x))) \)**: Now, we substitute \( f(f(x)) \) into \( f \): \[ f(f(f(x))) = f(a^2x + (ab + b)) = a(a^2x + (ab + b)) + b = a^3x + a(ab + b) + b \] Simplifying this gives: \[ f(f(f(x))) = a^3x + a^2b + ab + b \] 4. **Finding \( f(f(f(f(x)))) \)**: Next, we substitute \( f(f(f(x))) \) into \( f \): \[ f(f(f(f(x)))) = f(a^3x + (a^2b + ab + b)) = a(a^3x + (a^2b + ab + b)) + b \] This simplifies to: \[ f(f(f(f(x)))) = a^4x + a(a^2b + ab + b) + b \] 5. **Finding \( f(f(f(f(f(x))))) \)**: Finally, we substitute \( f(f(f(f(x)))) \) into \( f \): \[ f(f(f(f(f(x))))) = f(a^4x + (a(a^2b + ab + b) + b)) = a(a^4x + (a(a^2b + ab + b) + b)) + b \] This gives: \[ f(f(f(f(f(x))))) = a^5x + a^4b + a(a^2b + ab + b) + b \] 6. **Combining Terms**: We can combine the terms involving \( b \): \[ f(f(f(f(f(x))))) = a^5x + (a^4b + a^3b + a^2b + ab + b) \] This can be factored as: \[ f(f(f(f(f(x))))) = a^5x + b(a^4 + a^3 + a^2 + a + 1) \] 7. **Setting Equal to Given Function**: We know that: \[ f(f(f(f(f(x))))) = 32x + 93 \] Therefore, we can equate coefficients: \[ a^5 = 32 \quad \text{and} \quad b(a^4 + a^3 + a^2 + a + 1) = 93 \] 8. **Solving for \( a \)**: From \( a^5 = 32 \), we find: \[ a = 2 \] 9. **Substituting \( a \) to Find \( b \)**: Now substituting \( a = 2 \) into the equation for \( b \): \[ b(2^4 + 2^3 + 2^2 + 2 + 1) = 93 \] Calculating the sum: \[ 16 + 8 + 4 + 2 + 1 = 31 \] Thus: \[ b \cdot 31 = 93 \implies b = \frac{93}{31} = 3 \] ### Final Answer: The value of \( b \) is \( \boxed{3} \).
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