Given f, of, x, equals, minus, 4, x, squared, minus, 4, x, plus, 18f(x)=−4x

Question

2
−4x+18, find f, of, 9f(9)

Answer 1

To find \( f(9) \) for the function \( f(x) = -4x^2 - 4x + 18 \), we can substitute \( x = 9 \) into the function.

\[ f(9) = -4(9)^2 - 4(9) + 18 \]

Now, calculate \( 9^2 \):

\[ 9^2 = 81 \]

Now, substitute this back into the function:

\[ f(9) = -4(81) - 4(9) + 18 \]

Now calculate \( -4(81) \):

\[ -4(81) = -324 \]

Calculate \( -4(9) \):

\[ -4(9) = -36 \]

Now, combine everything:

\[ f(9) = -324 - 36 + 18 \] \[ f(9) = -324 - 36 + 18 = -342 \]

Thus, the final value is:

\[ f(9) = -342 \]