To find \( f(3) \) for the function \( f(x) = 9 - 4x \), you substitute \( 3 \) for \( x \):
\[ f(3) = 9 - 4(3) \]
Calculating that step-by-step:
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Calculate \( 4 \times 3 \): \[ 4 \times 3 = 12 \]
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Substitute that back into the equation: \[ f(3) = 9 - 12 \]
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Now perform the subtraction: \[ 9 - 12 = -3 \]
So, \( f(3) = -3 \).