If `f:RrarrR` is defined by `f(x)=5x+2`, find `f(f(x))`.

Answer

To find \( f(f(x)) \) where \( f(x) = 5x + 2 \), we will follow these steps:

### Step 1: Substitute \( f(x) \) into itself
We start by substituting \( f(x) \) into the function \( f \):
\[ f(f(x)) = f(5x + 2) \]

### Step 2: Apply the function definition
Now we need to apply the function definition \( f(x) = 5x + 2 \) to the expression \( 5x + 2 \):
\[ f(5x + 2) = 5(5x + 2) + 2 \]

### Step 3: Distribute and simplify
Next, we distribute \( 5 \) in the expression:
\[ = 5 \cdot 5x + 5 \cdot 2 + 2 \]
\[ = 25x + 10 + 2 \]

### Step 4: Combine like terms
Now we combine the constant terms:
\[ = 25x + 12 \]

### Final Answer
Thus, the value of \( f(f(x)) \) is:
\[ \boxed{25x + 12} \]