To find \( f(2x + 1) \) for the function \( f(x) = x^2 + 9 \), we first need to substitute \( 2x + 1 \) into the function.
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Start with the given function: \[ f(x) = x^2 + 9 \]
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Substitute \( 2x + 1 \) into \( f \): \[ f(2x + 1) = (2x + 1)^2 + 9 \]
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Now expand \( (2x + 1)^2 \): \[ (2x + 1)^2 = 4x^2 + 4x + 1 \]
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So we have: \[ f(2x + 1) = 4x^2 + 4x + 1 + 9 \] \[ f(2x + 1) = 4x^2 + 4x + 10 \]
Next, we calculate \( f(2 \cdot 2 + 1) \):
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First find \( 2 \cdot 2 + 1 \): \[ 2 \cdot 2 + 1 = 4 + 1 = 5 \]
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Now plug \( 5 \) into \( f(x) \): \[ f(5) = 5^2 + 9 = 25 + 9 = 34 \]
Thus, \( f(2 \cdot 2 + 1) = 34 \).
The correct answer is: 34