find the value of f(5), if `f ( x ) = 3 x^2 − 4x` ?

Options

A. 55
B. 65
C. 57
D. 45

Answer

To find the value of \( f(5) \) for the function \( f(x) = 3x^2 - 4x \), we will substitute \( x \) with 5 in the function and simplify.

### Step-by-Step Solution:

1. **Write down the function**:
\[ f(x) = 3x^2 - 4x \]

2. **Substitute \( x = 5 \)** into the function:
\[ f(5) = 3(5)^2 - 4(5) \]

3. **Calculate \( 5^2 \)**:
\[ 5^2 = 25 \]

4. **Substitute \( 25 \) back into the function**:
\[ f(5) = 3(25) - 4(5) \]

5. **Calculate \( 3 \times 25 \)**:
\[ 3 \times 25 = 75 \]

6. **Calculate \( 4 \times 5 \)**:
\[ 4 \times 5 = 20 \]

7. **Subtract \( 20 \) from \( 75 \)**:
\[ f(5) = 75 - 20 = 55 \]

8. **Final answer**:
\[ f(5) = 55 \]

### Final Result:
The value of \( f(5) \) is \( 55 \).

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